Despite the fact that the plots of the games usually appear barebone, Metal Slug has its fair share of characters, all of whom have a great deal of backstory to them. The backstory to each character is where the real plot points stand out.
Protagonists (Broken down by game appearance)
The main protagonist of the series, Marco joined the military's vocational school following technical high school, and after graduating, joined the Peregrine Falcons Squadron, soon becoming its leader. Though generally a good-natured guy, he tends to flip his shit whenever Morden is mentioned, given the fact that Morden was responsible for the deaths of many of his good friends.
Off the battlefield, Marco is an expert computer technician, often creating computer viruses for fun, but one in particular that unintentionally made its way onto the net infected the military's mainframe, made it past all of the firewalls and almost caused the launch of several nuclear missiles. He intends to take that secret to his grave.
From Metal Slug 6 onward, Marco's unique ability is to deal double damage with his handgun. If playing on Easy, though, this ability transfers over to the automatic Heavy Machine Gun. In Metal Slug 7/XX, he can also use the Burst Shot, which allows for rapid fire, though he can't move.
Marco Rossi's Tropes:
- All-American Face: More or less designed as the typical American war movie hero.
- Berserk Button : Anything involving General Morden, due to the latter killing many of his comrades during his attacks.
- Big "NO!": He lets out one for his death cry.
- Boring, but Practical: His ability in the later games is dealing double damage with a handgun. While this is hardly flashy, it's invaluable whenever you're without any upgrades. In Defense, his special is to shoot his Heavy Machine Gun, which is hardly flashy but a good all-purpose skill.
- Eagleland: He's a tanned, blonde-haired American who loves big guns and justice.
- Emergency Weapon: Starting in 6, he is focused on making the starting peashooter of a handgun not so pathetic. By dealing double damage, it's actually pretty decent. Another weapon is still preferable, but not as much.
- Extendo Boxing Glove: An alternate melee attack for when he's crouching.
- Handguns : His attack power is doubled while firing a handgun.
- The Hero: The leader of the team and the poster boy of the series.
- Heterosexual Life-Partners: With Tarma, who has been with him since the very beginning.
- "Open!" Says Me: An alternate melee attack when he opens chests is to simply kick them open.
- Overprotective Dad: Put a programming lock on ALICE to keep certain adult terms, particularly those dealing with charm and seduction, from even entering her vocabulary.
- Playful Hacker : During his spare time. He accidentally almost launched nuclear weapons at one point.
- The Smart Guy: Outside the battlefield he's an expert hacker.
- Truly Single Parent: He's the "father" of MS-ALICE.
- Vitriolic Best Buds : With Tarma
- Weapon of Choice: The Heavy Machine Gun, but initially it was the standard Pistol.
Son of a military man, he entered the Special Forces Training School after finishing junior high. At age 20, he joined the Peregrine Falcons on a mission to rescue the president, at which point he met Marco, the two becoming fast friends. When he found out Marco had been selected to take part in the counteroffensive against Morden, Tarma was quick to volunteer. Though he often pokes fun at Marco, he holds his friend in the highest regard.
Whenever he's not engaged in battle, he builds custom motorcycles with such attention to detail that he puts most professionals to shame. If and when he can retire from active service, he intends to open his own motorbike shop.
Tarma's engineering skill from Metal Slug 6 onward allows him to make better use of the Slugs that he comes across. They can take twice as many hits, he can use the vulcan fix, the vulcan's damage is increased, and he obtains twice as many Slug Shells on pickup. In 7/XX, he can also kick Slugs, which can either recover or damage them. However, the double durability and recovery/damage kick only works on Vehicle Slugs.
Tarma Roving Tropes:
- Ace Pilot: His specialty on the team starting in 6. He's the best at handling vehicles and it translates to gameplay as tougher vehicles, stronger weapons in them, and new abilities.
- Badass Biker: Off-screen. The Cool Shades and his backstory of expertly building bikes establish him as this.
- Cool Shades: Never seen without his shades. It also helps distinguish him from Marco at a glance.
- Demoted to Extra: Becomes a supporting character in 4, but regains his playable status in 5.
- Gadgeteer Genius : He's the team's Slug expert, largely due to him tinkering with vehicles in his spare time.
- Glass Cannon: In Defense, he has the lowest HP of the four main characters but his Shotgun does the most damage.
- Heterosexual Life-Partners: He's the only character who has been with Marco from the beginning.
- Meaningful Name: As the Metal Slug technician of the team, his name last name is Roving.
- The Lancer: Marco's best friend and foil, as well as the default player 2.
- Obligatory Swearing: F-Bombs upon player miss. Some console releases alter the game so that he shares Marco's death cry.
- Percussive Maintenance : His Slug Kick. Sometimes averted, causing damage to the Slug instead.
- Vitriolic Best Buds : With Marco.
- Weapon of Choice: The Shotgun.
Metal Slug 2
Eri was found abandoned on the steps of a church. When she became wise to the ways of the world, she eventually ran off and became the leader of a gang of street kids. The Intelligence Department of the Regular Army noticed her leadership skills, and thus recruited her. She went on to receive spy training, and took part in a number of missions requiring assassination. She found these types of missions distasteful, and requested a transfer to the SPARROWS division. Given her impressive track record, it was approved. Once transferred to the SPARROWS division, she was assigned the role of team demolitions expert.
Given Eri's background of growing up among street children, her demeanor and attitude in life mostly boils down to "Rely on nobody but yourself."
Eri's unique talent from Slug 6 onward is handling grenades. She starts each life with 20, gains double grenades on pickup, deals more damage with them, and is the only one able to aim her throws, which includes straight upward.
Eri Kasamoto Tropes:
- Action Girl: Kicks as much ass as any of the men.
- Badasses Wear Bandanas: She always wears one in nearly every appearance.
- Bare Your Midriff: Setting a trend, her military "uniform" exposes her belly.
- Brutal Honesty: In her first mission with Fio, Eri was blunt saying that her inexperience in combat was going to get them both killed, and that Fio was better hanging back so Eri could go on alone.
- The Big Girl: While the whole team packs plenty of power, she's the explosives specialist.
- Compressed Hair: Hidden in her bandana in her sprites. Some pieces of official art would have some of her hair spew out of her back head.
- Dark and Troubled Past: We need to reiterate that her old career as an espionage agency assassin was somehow so "distasteful" that she compared it unfavorably to blowing people up with grenades and flamethrowers.
- Demoted to Extra: Becomes a supporting character in 4, but regains her playable status in 5.
- Hard-Drinking Party Girl: She loves to drink spiritas (a 96-proof vodka).
- Heterosexual Life-Partners: With Fio.
- Informed Loner: She's on a four person team by the time of her introduction and does little to show off her loner personality. Made more apparent in Attack, where one of her strongest memories is abandoning Fio on her first few missions because she was too slow.
- In-Series Nickname: "Memphis Bomb Princess".
- Japanese Delinquents: A variation. Eri was a former sukeban (female gang leader) and she still sports blond hair.
- Kick Chick: She can sometimes use kicks as a melee attack animation.
- Mukokuseki: While she does have (light) brown eyes, her hair's a shade of blond that is anything but Asian, let alone Japanese (she's from Hiroshima). It is unknown if her blond hair was a leftover of her childhood as a sukeban.
- Sdrawkcab Name: Spelling her name backwards in Hiragana will get the name of a famous Japanese pop star Rie Tomosaka.
- Stuff Blowing Up: Starting in 6 her specialty is grenades.
- Tomboy and Girly Girl: Eri's the Tomboy. Her backstory, attitude, and appearance are much tougher than Fio's.
- Weapon of Choice: The laser.
- Younger Than They Look: Eri's two years younger than Fio, considering Eri's tougher personality.
Daughter of the massively wealthy Germi Family, hailing from Italy. The Germi family has historically been a military family, sending their oldest into service, so naturally her father wished for a healthy son to carry on the name. However, following Fio's difficult childbirth, her mother was unable to bear anymore children, making it the first time the Germi heir was female.
Eri's polar opposite, Fio was raised in a loving family, and has a cheerful and upbeat demeanor. Aside from her soldier training, she also studied chiropractics, acupuncture and moxibustion in university, and hopes to become a sports doctor in the future.
Fio's special trait from the sixth game onward is carrying extra ammo for her weapons. She starts each life with a Heavy Machine Gun, and gains 50% more ammo on weapon pickup. If playing on Easy, though, she automatically gets the Big Heavy Machine Gun as her initial armament.
Fio Germi Tropes:
- Action Girl: No less a capable fighter than any of the men.
- Badass Adorable: Best exemplified by her victory animation of her falling down coquettishly. Mind you, this is after wiping out hundreds of enemy troops.
- Bare Your Midriff: As is the norm with female fighters in the Metal Slug universe.
- Dare to Be Badass: Eri's cold abandonment on their first few missions together basically had this effect on Fio, as shown in Metal Slug Attack. Eri's willingness to call out Fio for being weak when she's spent her entire life being coddled is what pushed her into becoming as competent as she is now. That being said, she usually retains her meek demeanor off the battlefield.
- The Chick: The medical expert of the team and also the most emotional.
- Finger Poke of Doom: Her melee attacks include swift tonfa strikes, hatchet slices, and prissy slapping and shoving. Enemy soldiers die horribly all the same.
- Girly Bruiser: A hardened killer whose hobbies include embroidery and ballroom dancing.
- Guest Fighter: She is playable in The King of Fighters: Maximum Impact 2.
- Heterosexual Life-Partners: With Eri.
- Heroic Self-Deprecation: She usually thinks less of herself in comparison to her teammates.
- Last of Her Kind: Fio's parents' greatest fear. See Stay in the Kitchen below.
- Meganekko: An archetypical example in video games. She's got the cute look, modest personality, and is overall moe because of it.
- Miss Fanservice: A lesser one compared to Sofia, but far better known among fans. Cute girl with with a nice figure (which is obvious on any piece of official art, especially next to the modestly endowed Eri).
- More Dakka: Her Specialty from Metal Slug 6 onwards. The Heavy Machine Gun is basically her default weapon.
- Nice Hat: She wears one in almost every appearance.
- Older Than They Look: Despite her appearance and character, Fio is two years older than Eri.
- Revolvers Are Just Better: Her basic handgun is actually a revolver, though it does the exact same amount of damage as the other protagonists' pistols.
- Shock and Awe: A version of her in Attack uses a Thundercloud and a Chain Lightning gun. Thing is, Fio is afraid of lightning. An entire Ops storyline is dedicated to her overcoming her fear to use it.
- Small Girl, Big Gun: The heavy weapons specialist is the smallest of the four main playable characters.
- Stay in the Kitchen: Fio'a father would rather she not be in combat so damn much. Whether it's because she's a woman or because she's an only child (Last of Her Kind and thus putting the whole family line in danger since she has no children of her own) is up for debate (possibly both).
- Took a Level in Badass: She's normally the meekest of the main cast, but at the end of Metal Slug 3, she stands in a very proud manner atop of a floating Metal Slug. Eri, in comparison, has a hunched demeanor.
- Tomboy and Girly Girl: Fio's the Girly Girl compared to Eri's Tomboy. She's got a sheltered background, cuter looks, and is much less hardened in general.
- Weapon of Choice: The Rocket Launcher, but initially it was the Heavy Machine Gun.
- Wimp Fight: Believe it or not, this is one of her melee attack animations, but it's subverted in that it can damage or even kill any human-sized enemy with her sissy flailing.
Metal Slug 4
Initially, Nadia wanted to go into the modeling business, but she couldn't stop eating, which meant she kept gaining weight, so she enlisted into the Regular Army for the exercise. She soon discovered her skills as a soldier, and was chosen to help in stopping the Amadeus Syndicate from releasing its supervirus. Here, Nadia was a stand-in for Eri, who had been assigned to other duties. The one thing putting her apart from Eri is that her alternate melee weapon is a souped-up taser, capable of shredding the enemy. Unfortunately, due to some in-game bugs, she doesn't get as many points for using her melee.
Nadia Cassel Tropes:
- Action Girl: Runs and guns with the best of them.
- Bare Your Midriff: Not that it isn't a standard with the Regular Army in general.
- Big Eater: Compared to the other characters whose powerup relies in eating, she takes it Up to Eleven. Her idle animation almost always leads her grabbing a bite on a chocolate bar.
- Formerly Fat: Well, except the ending has her eating a big feast alongside the other heroes.
- Gainaxing: Whenever she does her close-range attack in her Valentine's Day outfit.
- Girly Bruiser: Especially her Valentine's Day outfit in Defense and Attack. This doesn't stop her from kicking ass, though.
- Girlish Pigtails: As evidenced by the fact she joined the military not to prove herself, defeat evil, or a love of fighting, she's just a girly girl who joined for girlish reasons. Her hair is appropriately in pigtails.
- Mundane Utility: Joining the military in the midst of conflict seemed like an easier way to lose weight than eating less.
- Rose-Haired Sweetie: She's definitely the cutie and probably the least militaristic of the protagonists, fitting her pink hair.
- Spy Catsuit: "Special Nadia's" outfit.
- Signed Up for the Dental: Joined the military as a way to exercise and lose weight.
- Significant Green-Eyed Redhead: Rose-Haired Sweetie with green eyes in her portrait.
- Stun Guns: She uses a taser as her melee attack.
- Set Swords to "Stun": Inverted. Her taser is set to essentially killing her victims outright like the rest of the team's melee attacks.
- Suspiciously Similar Substitute : To Eri, in terms of animations.
- Weight Woe: The reason she joined the military is to lose weight, going up her needs to become a supermodel. Unfortunately this gets conflicted to the fact when she's admitted to be a known Big Eater.
Trevor received his first computer at age three. By the time he was seven, not only could he perform complex coding, he also worked on creating antivirus progams during summer break, many of which are still in use at the school he attended. When he ended up joining the Peregrine Falcons, he found a great deal of respect for Marco, whose own computer skills surpassed his own. Here, he acted as Tarma's stand-in. His melee involves kicking the enemy so hard, it shreds them apart; he gains double points for this, but he has to hold still.
Trevor Spacey Tropes:
- Armed Legs: His melee is a powerful kick called Knife Boots.
- Asian and Nerdy: Korean and a Playful Hacker.
- Bishōnen: Compared to the other male characters, he's young and boyishly handsome.
- Child Prodigy: Literally owns and uses a computer since he was three years old.
- The Cracker: Zigzagged with Playful Hacker. Becomes the Regular Army's support hacker and a sideline commando.
- Nonstandard Character Design: Sprites-wise, Trevor is the only male who normally has sclera around the pupil (most have Black Bead Eyes).
- Oblivious to Love: More like he doesn't know that Abigail blushes at the sight of him.
- Playful Hacker: A point which causes him to get along with Marco, another playful hacker.
- The Smart Guy: An ingenious hacker.
- Suspiciously Similar Substitute : To Tarma, who was not playable in his game.
- Weapon of Choice: The Two Machine Guns.
Metal Slug: 2nd Mission
A recruit in the Peregrine Falcons squad who while on his way to investigate the Rebel Army's goals stumbled upon startling info from a rescued hostage: the rebels have made contact with aliens! After his requests for backup were ignored, he reluctantly decides to face the enemy himself.
- Expy: Of Tarma, sans shades.
A member of the Government Forces' Special Forces. Like Gimlet, she too stumbled upon info regarding the Rebels making contact with aliens while investigating a UFO sighting. After learning that Gimlet has decided to engage the enemy, she gives chase, not wanting to be beaten to the action.
- Expy: Of Fio, except she wears red. And doesn't wear glasses.
Metal Slug Advance
Walter joined the Peregrine Falcons squad with the hopes to train his mind and body, knowing he had the stamina to keep up with the rest of them. However, he never would've guessed his initial "training" would turn out to be a rescue mission.
Walter Ryan Tropes:
- Falling into the Cockpit: An early training mission became a very real mission as his drill instructor turned out to be The Mole.
- Mama's Boy: His hobby is listed as "phoning his mama."
- Palette Swap: To Marco.
- Suspiciously Similar Substitute: Again, to Marco as the main "guy" character.
- Weapon of Choice: The Drop Shot.
- You Gotta Have Blue Hair: His hair is literally blue. No mention is made of this.
Tyra's strong desire to fight evil is what motivated her to join the Peregrine Falcons alongside Walter. After getting the highest score on the written test, she was immediately put to the physical training course on the island where the game takes place.
Tyra Elson Tropes:
- Bare Your Midriff: Not normal combat attire, even for a trainee.
- Falling into the Cockpit: An early training mission became a very real mission as her drill instructor turned out to be The Mole.
- Palette Swap: She uses an edited version of Nadia's sprites.
- Revolvers Are Just Better: Defaults to a revolver, as shown in her official art.
- The Smurfette Principle: The only female to be a member of the PF Squad. Every other female is on the SPARROW Squadron.
- Suspiciously Similar Substitute: Has the same outfit as Nadia, her hair is also a red hue, and introduced as a new female character along side a new male character.
- Weapon of Choice: The Super Grenade Launcher.
Metal Slug Mobile
- Ascended Fanboy: Was overjoyed to work with Fio, one of his favorite soldiers.
- Bash Brothers: Works with Leona in games he stars in. In Metal Slug Attack, he is partnered with Fio.
- Limit Break: The Roberto Combination, which is a set of shots from his gun and some bomb throws.
- Trauma Button: Gets overly suspicious to any beautiful woman he gets in contact with. This is because, in his first mission, he once got frozen by Beatriz posing as a helpless civilian.
- Dramatic Wind: Her victory animation has Alisa removing her hat and letting the wind blow her hair out no matter the location.
- Hammerspace Parachute: She can deploy as many as she pleases.
- Identical Stranger: Her Metal Slug Defense artwork has her similarly designed as Fio.
- Improbable Weapon User: Uses a wrench as her melee attack.
- Weapon of Choice: The Big Rocket Launcher.
Ralf and Clark, in between their appearances in The King of Fighters series, appeared alongside the core team for Metal Slug 6, and are back for Metal Slug 7/XX. Joining them in XX is Leona and later Whip and Heidern in Metal Slug Defense. A better amount of information about these five can be found on their respective series' page.
Ikari Warrior Tropes:
- Canon Immigrant: They originally came from Ikari Warriors (Ralf and Clark) and The King of Fighters (Heidern, Leona and Whip) before making the jump to Metal Slug.
- Hired Guns: Unlike the rest of the Regular Army, they're not part of the group; they're a mercenary squad offering their services to them.
- Debut: Metal Slug 6
Aside from his participation in various fighting tournaments, little to nothing else is known about him or Clark. There's rumors flying around, but he tends to ignore them.
Though carrying half as much ammo and grenades as anyone else, Ralf makes up for this with his Vulcan Punch, capable of destroying tanks, and his melee speed is much faster than anyone else's (and his normal melee can also damage things that others cannot). He's also the only character capable of taking two hits. He's just that tough.
Ralf Jones's Tropes:
- Dash Attack: His other special move, the Galactic Phantom Punch.
- Heterosexual Life-Partners: With Clark.
- Hot-Blooded: The guy is willing to charge a tank with his bare hands.
- Knife Nut: Collects knives as a hobby. Though ironically he's one of the few that doesn't use them on the battlefield.
- Lightning Bruiser: He can run and jump as well as everyone else, has fast (and highly damaging) melee attacks, and takes 2 hits to kill, unlike most of his allies.
- Made of Iron: Why can he take a tank shell? Just because he's that damn tough.
- Older Than They Look: He was born in 1992, making him 13 years older than both Marco and Tarma, 16 years older than Fio, 18 years older than Eri and about 40 years old by the time of his first appearance. Official art still depicts him as looking just as young as Marco and Tarma.
- One-Hit Point Wonder: Averted; he can take two hits. That said, certain things can still One-Hit Kill him, such as getting eaten by Man Eaters.
- Rapid-Fire Fisticuffs: His special move, the Vulcan Punch.
- Red Oni, Blue Oni: The red to Clark's blue.
- Weapon of Choice: The Flame Shot.
- Debut: Metal Slug 6
Clark and Ralf have been longtime friends, even in the unit the two of them are assigned to.
Clark's unique ability is his Super Argentine Backbreaker, a special melee move capable of earning him a lot of points in a short time frame. He also gains a small window of invulnerability with each enemy he tosses with this. However, it only works on certain human-sized enemies.
Clark Still's Tropes:
- Cool Shades: Much like Tarma. Echoing Tarma's relationship with Marco, the shades serve to differentiate Clark and Ralf.
- Difficult, but Awesome: If you can overcome its short range, the Super Argentine Backbraker will rip nearly any hoarde of (human) mooks a new one, earning you tons of points and a lot of invincibility time.
- Hammer Space: In Defense, his special move is to pull out a large Exploding Barrel and hurl it. In Attack, his "Jet Clark" variant throws refrigerators.
- Heterosexual Life-Partners: With Ralf. They've been together for years in several combat theaters.
- Red Oni, Blue Oni: The blue to Ralf's red. He's less hot blooded and more stoic.
- The Stoic: Even when suplexing enemy soldiers, he's not exactly a Screaming Warrior.
- Stone Wall: As Jet Clark, his ability to throw refrigerators to use as blockades make him very hard to wear down.
- Wrestler in All of Us: His Backbreaker.
- Weapon of Choice: The Iron Lizard.
- Debut: Metal Slug XX
Leona was adopted by Commander Heidern following her involuntary transformation and slaughter of her hometown, and Clark and Ralf helped to oversee her training.
Leona joins the team for XX, but has to be unlocked via DLC (she's only 99 cents, well worth it). She carries an amalgamation of everyone else's skills (Stronger pistol fire, 20% more ammo and grenades, Slugs can take an extra hit, and she retains her weapons after losing a life. Interestingly, her special melee, Moon Slasher, can destroy bullets). According to her profile, Clark, Fio and Leona finished a mission that also further bonded the three as being good friends.
Leona Heidern's tropes:
- All Your Powers Combined: In XX, she has basically everyone else's special skills.
- Ascended Extra: Originally appeared in a cheap cell phone game before being moved to the main series.
- Cat Girl: By donning cat ears, she can decrease her hit points while increasing her attack.
- Close-Range Combatant: In Defense, her moon slasher is her only move.
- Guest Fighter: She originates from The King of Fighters series.
- Signature Move: Her Moon Slasher, originally from KOF is a chop attack that deflects projectiles.
- True Companions: With Ralf and Clark, ever since KOF '96.
- Debut: Metal Slug Defense
Whip makes her debut in Metal Slug Defense as part of the King of Fighters faction. Since the KOF faction does not exist in Metal Slug Attack, Whip has been moved to the P.F. faction.
- Cast Herd: Whip was separated from Ralf, Clark, and Leona in Defense, since the latter three are part of the P.F. faction. While she eventually joined alongside them in the same faction in Attack, Whip is not part of the Wrath team, rather being placed next to the Slugnoid Type-B for the Agent Sally team.
- Last Episode, New Character: Whip and Heidern were the final units implemented in Metal Slug Defense.
- Revolvers Are Just Better: Her special attack is shooting a bullet from a golden revolver. Its range is short in Defense and much farther in Attack.
- Whip It Good: Her standard attack. Her whip is able to cause knockback in Attack.
- Debut: Metal Slug Defense
Heidern makes his debut in Metal Slug Defense as part of the King of Fighters faction. Since the KOF faction does not exist in Metal Slug Attack, Heidern has been moved to the P.F. faction.
- Cast Herd: Heidern was separated from Ralf, Clark, and Leona in Defense, since the latter three are part of the P.F. faction. While he eventually joined alongside them in the same faction in Attack, Heidern is not part of the Wrath team, rather being placed next to the Donkey Slug (Eri) for the "Operation Ikari" team.
- Early-Bird Cameo: Appeared as a drill instructor in Defense's Combat School before becoming a playable unit.
- Hired Guns: The leader of the Ikari Warriors, who sends his troops to the Regular Army whenever there's a big conflict.
- Last Episode, New Character: Whip and Heidern were the final units implemented in Metal Slug Defense.
- Life Drain: His special attack has him jump and suck the life of the closest unit.
- Precision F-Strike: Go. To. HELL!
- Razor Wind: His long-range attack.
Antagonists (By faction)
- Debut: Metal Slug
The primary antagonists of the series, the Rebel Army was formed when Morden defected from the Regular Army over the death of his son. As he was A Father to His Men, they followed him out of sheer loyalty, and after merging with various terrorist groups, proved to be so dangerous that the Regular Army were forced to get their act together. Fanatics to the extreme, they would do whatever it took to overthrow the world's governments and install their own, even siding with alien invaders to get the job done. That said, they're certainly not stupid, and will side with the Regular Army to deal with threats far greater than them.
Rebel Army tropes:
- Armies Are Evil: Pretty much, though they're more comedic than your usual evil army.
- Army of Thieves and Whores: They certainly fit this trope after merging with the terrorist groups that had been plaguing the Regular Army for some time. However they all seem to get along pretty well and are zealous in their loyalty to Morden. Further shown in Metal Slug Attack, where multiple factions exist within the army, but they're all unified in their loyalty to Morden. Even the soldiers forced into conscription have been shown to eventually develop a loyalty to their squad.
- Determinator: You have to admit, even after half a dozen games of getting slaughtered by the heroes, it's impressive to see that they're still trying to take over the world in spite of all their setbacks.
- Enemy Mine: Though they oppose the Regular Army, they will join forces with them to deal with greater threats such as the Mars People and the Invaders.
- Laughably Evil: For an evil army, yep.
- Made of Plasticine: Applies to the mooks, since one bullet is all that's needed to take them down. Of course, you can keep shooting at them to earn more points until they fall over dead.
- Mascot Mooks
- Putting on the Reich: They resemble Those Wacky Nazis in their uniforms and flags.
- The Revolution Will Not Be Civilized: A gang of rebels who oppose the government, and they're portrayed as the bad guys.
- Stupid Jetpack Morden: Though they're not really Nazis, they still have some impressive war machines and weapons that can give the Regular Army a run for their money.
- Undying Loyalty: To Morden, since he was A Father to His Men.
- Villains Out Shopping: Some soldiers can be seen doing mundane things, such as sunbathing, sitting round a campfire or playing a handheld console.
- Debut: Metal Slug
Morden was formerly a Vice Admiral in the Regular Army Marine Corps. Though a tough and efficient commander, he was also something of A Father to His Men, which greatly earned him their respect.
Things went well for Morden, up until the Central Park bombing, which not only took away his right eye (hence the eyepatch he wears), but it also killed his young son. To twist the knife even further, he later found out that Regular Army Intelligence knew about the bomb threat and pushed for the high command to stop it, but due to rampant corruption in the system at the time, the higher-ups dismissed the threat as being a mere prank or so (later blaming the bombing on a lack of intel), which, when combined with his emotional instability and rampant alcoholism following afterwards, ended in Morden's resignation.
When Morden left, all of the soldiers under his command (including Allen O'Neil) followed him out of sheer loyalty to him. This allowed him to form the Rebellion Army, and he began making swift tactical moves against the Regular Army, nearly destroying them and finally motivating them to get their act together. In fact, during his attack on the president, he gained his nickname as the "Devil Rebirth", due to just how frightening he was.
Though he was a main threat in Metal Slug, in Metal Slug 2 it turns out he teamed up with the Mars People, who gave him the technology he needed, but were quick to turn on him. He barely showed up in games 3 (where a Mars Person was impersonating him) and 4 (there were robotic duplicates of him, possibly including the one in the intro demo), and was completely absent in 5, but made a return in 6, where he, again, made a pact with the Mars People, but this time, due to the Venusians invading, it was soon under different terms. Taking a certain route in Stage 4 will mean that he's the one who actually saves the player at the end of the game.
His biggest return to the spotlight was in 7/XX, where it turns out his own soldiers, from some unspecified time in the future, went back in time to help him out, again out of sheer loyalty to him.
- Arch-Enemy: To Marco, as he was responsible for most of Marco's comrades being killed in his attacks.
- Big Bad: For most games, though sometimes he gets the title hijacked.
- Big Damn Heroes: If you took the top path in Mission 4 in Metal Slug 6, he appears to save you from a great fall after the invader king dies.
- Butt-Monkey: Appearing on screen is usually a sign that he'll suffer a Humiliation Conga.
- Canada, Eh?: Hails from Canada, and has some hobbies that are stereotypical of Canadians like hunting and building log cabins according to his profile.
- Cigar Chomper: It's not shown in the games, but his profile reveals that he likes to smoke cigars before heading off to battle.
- Cool Plane: Despite being an army general, he seems to have a strong preference to copters and planes over tanks. The few times he is in a tank, its a method of defense, not hiding.
- Evil Laugh: Tends to laugh in a mocking tone upon approaching the player.
- Eviler Than Thou: Frequently on the receiving end of this.
- Eyepatch of Power: The man certainly looks imposing thanks to his eyepatch.
- A Father to His Men: Treated his men as if they were family, which lead them to follow him out of loyalty when he defected.
- Final Boss: Of the original and of 7/XX.
- Joker Immunity: Despite being defeated and/or double crossed whenever he appears, he always survives to lead his army again.
- Made of Iron: When riding in the Hi-Do in the first game, he can take even more bullets than Allen O'Neil.
- Not Me This Time: Against all expectations, he is not the main villain of 4. The Amadeus syndicate actually abuses this expectation, having robot copies of both Morden and Allen.
- Red Baron: "The Devil Reborn", a moniker he got during his attack on the president due to just how terrifying he was.
- Shadow Archetype: He could be seen as this to Heidern, since both were military men who lost their eye and loved ones to circumstances beyond their control (for Heidern, he lost his family to Rugal, and for Morden his son to a terrorist attack), the difference being that Heidern would go on to adopt Leona and move on from his past after Rugal's demise, whereas Morden...didn't.
- Villain Decay: Poor guy started to go down Dr. Eggman's path after 2. In fact, the only time he's been the Final Boss since then was 7.
- Villain Takes an Interest: One story in Attack has him take an interest in Leona's Orochi power after she underwent the Riot of the Blood, ordering Abigail to get samples from her and send them to Navy for further study.
- Well-Intentioned Extremist: Distraught over the death of his son in a terrorist attack that could have been prevented and angered at corruption in the Regular Army, he abandoned the Regular Army and formed his own terrorist group, the Rebel Army, and while he plans on removing corruption from the world, his ultimate goal is to create a world wide military dictatorship.
- Debut: Metal Slug
Morden's right hand man and bodyguard. When Morden resigned from the Regular Army, Allen, alongside all of Morden's supporters, followed him out. He's most remembered for taking insane amounts of punishment and supposedly being killed each game (he's eaten by an Orca in Metal Slug 2), only to return later. In Metal Slug 3, he not only died, but came back in the same level. Aside from being nigh unkillable, he also has a wife and son to return home to at the end of the day.
He appeared in Metal Slug 4's second and final stages, whereupon fighting him at the latter reveals him to be a machine, possibly meaning you also fought a robot Allen back in Stage 2. He comes back for Metal Slug 7/XX in a Rebel Gigant, still spouting his trademark quips and insults.
Allen O'Neil tropes:
- A Day in the Limelight: He's the player character for the (Japan Only) Metal Slug: Allen's Battle Chronicles game and its enhanced American port, Metal Slug Mobile 3.
- Assist Character: In the soldier minigame in 3's console port, he acts as the Rebels' "bomb" when summoned, shooting up any Martians that are in the way. He also shows up in 3's final mission proper during the clone corridor sequence helping the player fight off clones.
- Bald of Evil
- BFG: Wields a large machine gun whenever he's fought.
- Blood Knight: Yep. He even leads his own squadron in Attack called the "Allen Platoon", who are this trope to the extreme.
- Boss Banter:
- "C'MON, BOY!"
- "YOU'RE MINCEMEAT!"
- The Dragon: To Morden. Also doubles as The Brute.
- Duel Boss: He almost always provides the player with a Heavy Machine Gun before his fight, to be a match against his own. In 7 he wield a Slug Gigant, which is matched by the player's own Gigant (though the fact that the two use the same weapon is happenstance in this case). The one time he uses a clearly advantagous weapon without giving the player something to compensate, It turns out to be a duplicate.
- Eagleland: Type 2, a loud, boorish villain who loves to shoot stuff up with his gun.
- Engrish: "GO HOME TO MOMMY!"
- Even Evil Has Loved Ones: Has a son (Allen Jr., shown below) and wife, which according to Word of God is why he keeps coming back, so he can see them again.
- Evil Counterpart: To the player character, on the grounds of both characters having similar abilities (Heavy Machine Gun, grenades, melee attacks...), the difference being that he can take way more punishment before giving up the ghost as opposed to the player (who's a One-Hit Point Wonder).
- Heroic Build: Dude is frikkin' ripped. Too bad he's not really a hero (Enemy Mine situations notwithstanding)...
- I Shall Taunt You: Loves to throw insults at his foes as he fights them.
- Joker Immunity: Like Morden, he always keeps coming back, despite having been riddled with bullets and falling to his death in the first game, the second having him fall down to the ice water but apparently getting eaten by a giant Orca. The third game doesn't have anything notable besides him collapsing and falling about twenty feet, but his body still vanishes like regular enemies do after the fight. In Attack he gets impaled by Caroline's Augensterm and electrocuted in an Extra Ops story.
- Lightning Bruiser: Despite being bigger than the playable characters, he's also faster than them.
- Implacable Man: He cannot be stopped. Just shooting him alone is barely going to phase him.
- Improbable Weapon User: Get too close to him and he'll slap you with the ammo belt of his machine gun.
- Large Ham: He's the only character in the Metal Slug franchise to actually have spoken lines. And they are ALL taunts!
- Made of Iron: He's a human (except in 4), just like the player characters. Unlike the player characters, he has an obscene amount of health for a human, being able to last longer than a tank!
- Mirror Boss: He's basically similar to the player character, using a Heavy Machine Gun like yours, stick grenades, and even a melee attack. The difference is that you take one hit, he takes several.
- One-Man Army: See his Red Baron entry below.
- Red Baron: "Fearsome Army of Trillion".
- See You in Hell: His death cry.
- Turns Red: His skin turns red as he takes more damage and speeds up.
- Unexplained Recovery: All the time. Bonus points for Metal Slug 3 having him return during the attack on the Mars Peoples' Mothership despite you apparently killing him in the same level.
- Walking Shirtless Scene: Just look at him! He never wears a shirt, even in places like Siberia!
- Debut: Metal Slug 2/X
The leader of the Arabian forces, Abul Abbas made an alliance with the Rebel Army. After their defeat in mission 1, a few Arabian rebels show up in the beginning of mission 2 as a last ditch effort.
- Bad Boss: He has a terrible habit of refusing to own up to his own mistakes. In Attack he refuses to let his own troops stop to refuel their units, then blames them for running out of fuel at a critical moment.
- Dummied Out: Sprites of Abul attacking and setting up his white flag are present in 2's ROM. These get their use in Defense and Attack.
- Fat Bastard: Is noticeably overweight and is also a villain.
- Hoist by His Own Petard:
- I Shall Taunt You: Shows up multiple times commanding his troops and taunting the player.
- Know When To Fold Them: Waves a white flag once things go bad for him.
- Starter Villain: He serves as a first-level foe whose army is even worse equipped than the Rebels, and his troops lose all presence after the first level.
- The Unfought: The player ends up fighting the mission's boss while ignoring Abul in the background.
- White Flag: Raises one on his sword when he surrenders after things go south.
- Debut: Metal Slug 7/XX
Morden's own troops from an unspecified time in the future. Presumably at some time after Morden was captured or killed, his own forces, again out of loyalty, gathered up their technology and, though the construction of what appeared to be a time window or portal, went back in time to help Morden out. Despite having new weapons and upgraded machinery, they still got their asses handed to them, and with their window destroyed, they were unable to do anything else.
- Elite Mooks: Similar to regular Rebel grunts, except they wear blue and use futuristic weapons and vehicles.
- Make Wrong What Once Went Right: Their goal: give Morden the necessary resources to defeat the Regular Army and change history in their favour. Unsurprisingly, they fail.
- Trapped in the Past: Their ultimate fate after their time gate got destroyed.
- Debut: Metal Slug Advance
That's right, Allen's own son is here. He posed as a training instructor, which allowed him access to the island where the Peregrine Falcon trainees were undergoing the test. From here, he was able to lead some of Morden's forces to launch a surprise attack on the trainees, capturing the most of them and allowing Morden's troops to set up a base.
Unlike his father, though, Junior tends to act more strategically in direct confrontation against the player. However, once injured past a certain point, he eventually loses his temper and starts acting more like his father in battle. However, finding and defeating him is easier said than done.
Allen Junior's Tropes
- Generation Xerox: Just like his dad, though he does try to act smarter than him.
- In the Blood: He tries to act smarter than his father, and indeed becomes more successful in attacking the Regular Army than him, but in the end gives in to the same rage his father is known for.
- Like Father, Like Son: Get him mad enough, and he'll end up Not So Different compared to his papa.
- The Mole: He infiltrated the Regular Forces training camp by posing as a drill instructor.
- Pistol-Whipping: One difference from his father is that he does not typically use a knife, instead preferring to slam his opponent with his ammo belt, which is one of the few non-lethal attacks in the game.
- Debut: Metal Slug 2/X
Aliens from Mars, if that wasn't obvious enough (though they do resemble squids, according to some). Possessing spaceships straight out of a 50's B-movie, they allied themselves with Morden, but were really using him to weaken Earth's defenses so they could take over with little to no opposition. Though defeated at the end of 2/X, they kidnapped Morden before the events of 3, sending a Mars Person to impersonate him, and eventually capturing one of the player's characters and creating clones of him/her.
At the onset of Metal Slug 6, it appears as though they've allied with Morden again, but this time it was to find their leader, Rootmars. Unfortunately, the Invaders showed up before Rootmars could be fully extracted, and they spent the rest of the game imprisoned at the Invaders' lair, if they weren't outright killed or eaten.
Taking a certain route in Stage 5 of 7/XX will show that the Mars People are back, and at the end of the game, just as Morden is about to be taken into custody, the Mars People swoop down and take him to safety.
Mars People Tropes:
- Aliens Are Bastards: They just want to conquer and destroy without much backstory.
- Alien Blood: They bleed green.
- Brain in a Jar: The Ring Laser Mecha units are operated by a brain in a jar.
- Chronic Backstabbing Disorder: They betray Morden twice, for no reason other than because they can.
- Enemy Mine: They team up with both the Rebels and the Regular Army to fight an even greater threat, the Invaders.
- Expy: They look exactly like H. G. Wells' martians.
- Flying Saucer: Their main vehicle. Some of their units are unmanned ones that fire a laser. Their mothership is an even bigger one.
- Giant Space Flea from Nowhere: In Metal Slug 2. Not so much in X, where they are foreshadowed better.
- Hoist by His Own Petard: Both their betrayals of Morden and the Rebel Army lead to an Enemy Mine that causes their defeat. The first time because a pilot from the Rebel Armor rams their mothership and forces it to retreat, the second because the Rebel Army provides the player character with a rocket that allows them to reach their mothership.
- Homing Projectile: Martians primarily attack with three homing nuclei-like projectiles. Thankfully said projectiles are destructible.
- Last Episode, New Character: They show up in the last level of 2. Averted in X where they appear in earlier levels.
- Oh, Crap!: Their standard reaction when the Invaders show up.
- Ray Gun: They wield these, just like classic aliens...although said guns tend to fire out slow, homing, destructible nucleus-like projectiles.
- Starfish Aliens: They resemble giant jellyfish/squid. Yet they have skulls, green blood, and mouths.
- The Worf Effect: After establishing themselves as the premier threats of 2/X and 3, they're easily taken down, captured and imprisoned, and even eaten for breakfast by the Invaders in 6.
- Debut: Metal Slug 3
The leader of the Mars People, who orchestrated the events of 2/X and 3. Though originally looking like a larger Mars Person (just wearing a see-through helmet), his real form was revealed after his spaceship was destroyed (and it looked an awful lot like E.T.) He was defeated at the end of 3, with his brain being blown out, and sank into the ocean floor, presumably deceased.
At the beginning of Metal Slug 6, Morden and the Mars People were looking for Rootmars, and just as they located him, the Invaders came in. It turns out that while Rootmars was on the ocean floor, he had apparently recovered from his freefall beating at the hands of the team, and learned a lesson as well. During Stage 4, if you take the alternate route, Rootmars will swoop down and grab your player, taking him or her to the next destination whilst also being outfitted with two gatling guns, helping take down the Invaders. Taking this route also means Rootmars saves you at the end of the game.
- Big Bad: He is the main villain of 3.
- Big Damn Heroes: If you took the bottom path in Mission 4 in Metal Slug 6, he appears to save you from a great fall after the invader king dies.
- Eldritch Abomination: He may look like E.T., but also looks like something out from H.P. Lovecraft's work.
- Enemy Mine: Rootmars is willing to cooperate with both the Rebels and the Regular Army to fight an even greater threat, the Invaders, and even becomes playable to an extent in 6.
- Evil Laugh: Lets a high-pitched crackle as it grabs the player's SV-001. He also does this again when the player take the alternate lower route in mission 4 of 6.
- Foreshadowing: One of 6's cutscenes shows the Morden-Martian alliance trying to recover something out of the sea before the Invaders attack. This is in fact Rootmars.
- Final Boss: Of 3.
- Free-Fall Fight: He is fought while you and the soldier you rescued (and another player, if any) fall down to Earth.
- Good Scars, Evil Scars: He has a number of Frankenstein-like stitchings on him.
- Greater-Scope Villain: Rootmars is the one who masterminded the alien invasion in 2/X but was not seen in the game. You do fight his mothership, however.
- Large and in Charge: The normal Mars People are human-sized, Rootmars takes up most of the screen you fight him on.
- My Brain Is Big: Bonus points for it actually being visible, encased in a dome.
- Power Floats: Likely owning to his psychic powers, Rootmars is always seen letivating on his own.
- Promoted to Playable: In Metal Slug 6's fourth stage, taking the bottom path allows you to ride Rootmars and you control both his hand and a cannon attached to his head. Using the Bomb button causes him to use his brain wave as a Smart Bomb.
- Psychic Powers: Fitting for an alien with a giant brain, he has psychic powers.
- Super Intelligence: Part of the reason he is the leader of the Mars People.
- Debut: Metal Slug 5
A mysterious paramilitary group who attacked a Regular Army base and ended up stealing blueprints on Rebellion Tech, including that of Metal Slugs, which led to them creating their own bastardized and upgraded versions. Due to the confusing nature of the game (and the fact that so much went unused), it was hard to tell who was really in charge. It appeared as though they had gained the trust of the natives by the Corridor of Fire, and was using them to keep intruders away.
Ptolemaic Army Tropes:
- Expy: Of the Rebel Army. Most of the enemies are even edits of Rebel soldier sprites. They're also one to the Brotherhood of Nod.
- Gas Mask Mooks: The Ptolemaic Special Forces wear black body suits with gas masks on them.
- Knight of Cerebus: While Metal Slug 5 has most of the series usual silliness, the Ptolmaic Army's typical soldiers lack the silliness of the Rebel Army.
- Power Copying: They specialize in stealing technical plans from the Regular and Rebel Army.
- Religion of Evil: They are led by Ptolmaic Shamans, and apparently worship Avatar of Evil.
- Debut: Metal Slug 5
- Attack of the 50-Foot Whatever: Aside from the Mars Peoples' mothership (which is big enough to serve as an entire stage), it is easily the largest boss in the series, which is no small feat by any means.
- Autobots, Rock Out!: The battle against the Avatar of Evil has a heavy metal remix of the "Final Attack" theme.
- Background Boss: Spends most of the fight in the background, and you have to shoot the glowing skull on its chest. Averted in Attack, where it acts like most units and fights in the foreground.
- Big Bad: It is presumably the main villain for 5, but we may never know.
- Bullet Hell: Downplayed in 5, but its appearance as a unit in Attack plays it straight, where it fires an obscene amount of energy shots as its main form of attack.
- Celestial Body: Its entire body seems to be made out of the fabric of space.
- Dramatic Thunder: Thunder and lightning strikes when the boss makes its appearance.
- Eldritch Abomination: A gigantic demonic creature that looks like it was made from the fabric of space itself. It also has a skull in its chest that serves as its weak point. In Metal Slug Attack, even the scythe it weilds gets in on it and appears to be organic - and the aforementioned skull appears to be portruding out of its chest, breathing on its own.
- Emotion Eater: According to Mira, the Avatar of Evil grows stronger by feeding on human emotions.
- Evil Is Bigger: Barring Rugname, the Mars People's mothership, this thing is by far the largest boss in the franchise.
- Final Boss: With 5 allegedly being the last in chronology, the Avatar of Evil serves as this for the series plot, as well as the last boss for 5 in general.
- Flaming Skulls: The skull in its chest seems to be burning with an ethereal or cosmic substance.
- Generic Doomsday Villain: Even by the standards of this series.
- Giant Space Flea from Nowhere: There is no explanation if this entity was allied with the Ptolemaic Army, or if it was their leader, or if they were a Religion of Evil and its their God of Evil they were summoning to bring about The End of the World as We Know It. Attack seems to point to the latter, as Ptolemaios summons it for his special attack, and later cements it by having the Avatar of Evil be the "Ultimate Boss" of the Ptolemaic Army. Prior to its inclusion as a unit, this entity didn't even have a name.
- Hell Is That Noise: Produces a loud screech when it shows up to attack you in 5, as well as when it's finally defeated.
- Knight of Cerebus: Whatever this thing is, its design is very much Darker and Edgier compared the usual bosses that appear in the series and is actually very menacing.
- Lean and Mean: The silhouette shows that it is a very thin being.
- Made of Evil: It is even in its name.
- Non-Standard Character Design: Whereas everyone else is a human, an alien or a robot, this thing is a towering entity thats made of space.
- Playing with Fire: Most of its attacks will burn you to death should they hit.
- Red Eyes, Take Warning: It has a piercing gaze with red eyes.
- Screw This, I'm Outta Here!: When defeated, it flies back into what is presumbably its home dimension.
- Sinister Scythe: Which appears to be forged out of flames.
- Sinister Silhouettes: In 5, it is pitch black for the majority of its screentime, only shown off by the thunder strikes.
- Winged Humanoid: It has large, bat-like wings.
- Debut: Metal Slug Attack
Originally meant to be the Final Boss of Metal Slug 5, Ptolemaios makes his true debut in Metal Slug Attack as the main villain for the "Ptolemaic Attack" event. He is the leader of the Ptolemaic Army, controlling his troops within the shadows. He uses Sol De Rokker's red jewel to create a tower for himself that attacks with lightning and rosetta stones.
A side story revolves him annihilating the Red Goblin society, with Red Goblin seeking revenge.
- Bad Future: Ptolemaios is implied to be the winner in a future timeline. This results in two other characters going back in time where Ptolemaios has lower amounts of power.
- Big Bad: Informally in 5. In Attack, he is this to Red Goblin.
- The Cameo: Mostly unintentional, but his towers (as well as the Stone Turtle and the Elephants) can be seen in the background of Mission 5.
- Came Back Strong: Every death he suffers results in him getting new attacks.
- Death from Above: Drops Rosetta stones on top of the opposing team.
- Dummied Out: A nearly complete set of sprites is present in Metal Slug 5. Most of them are given use in Attack.
- Hijacking Cthulhu: His Abyssal form's special attack is summoning the Evil Spirit Incarnate.
- Luke, I Am Your Father: "Diaphtora Genesis" reveals that Mira is his daughter.
- Shadow Dictator: How his description in Attack handwaves his lack of appearance in 5.
- Shock and Awe: The bottom of his tower produces lightning strikes.
- The Unfought: Was intended to have a boss fight near the end of the game, but it was Dummied Out.
- What Happened to the Mouse?: Due to 5's rushed state.
- Debut: Metal Slug 6
The Mars People's nemesis, they not only appear to be physically stronger and more diverse than the Mars People, they also seemed to have better technology on their side as well. They formed the second half of Metal Slug 6's plot, especially after their first appearance was snatching up two martians and eating them.
Their king came to Earth via an asteroid, and was quick to set up an underground shelter for him. After one hell of a fight against the team, the king fell to his death, releasing an explosion that apparently killed the protagonists as well. Depending on which route you took in Stage 4, either Morden or Rootmars will save the player.
- Alien Blood: They bleed purple, in contrast to the Mars Peoples' green.
- Aliens Are Bastards: Even moreso than the Mars People.
- Always a Bigger Fish: Right when both Morden and the Mars People have you captured, these guys then come in and make very short work of them. It even extends to the flashback where they make very short work of both the Rebel troops and Mars People.
- The Dreaded: The Mars People cower in fear when these guys appear. And rightfully so.
- Evil Is Visceral: They have an organic lair as opposed to the Mars Peoples' technological one.
- Food Chain of Evil: The Invader hunts the Mars People and serves as an arch-nemesis for them.
- Giant Enemy Crab: The Crab-tanks and Vanguards.
- Knight of Cerebus: The Mars People have an Oh, Crap! reaction when they show up and eat them at the end of Mission 2. The final mission also has a Dark Reprise of the classic "Final Attack" theme.
- Heli-Critter: The Smashers, which spin their legs to fly in the air like a helicopter before inflating themselves to crash down on you.
- Horde of Alien Locusts: Literal in this case, as most of them are insectoid in nature, and they come in droves.
- Horrifying the Horror: The Mars People who were the dangerous main antagonists of 2/X and 3 are deathly afraid of them, cowering at first sight of the basic Invader drones.
- Puppeteer Parasite: One of the Invader units is a small flying parasite-like bug that latches onto the heads of rebel troops and mind-controls them. In the final stage, a unique variant appears to have mind-controlled one of the non-selected player characters into fighting against the players.
- Spin Attack: The Drones move around via spindashing.
- To Serve Man: Invader Drones don't just eat Martians. Some of them can throw their neck forwards and will eat the player character whole if it connects.
- Unique Enemy: There is a golden Hunter Walker encountered if you take a secret path in the final mission, killing it grants 50000 points.
- Zerg Rush: The standard troops ambush in groups. In Mission 3, a large horde of them come spinning down from the right side.
- Debut: Metal Slug 6
A huge alien that serves as the final boss of 6, and the leader of the Invaders.
- Background Boss: Most of the boss is in the background. You need to attack his head to damage him.
- Big Bad: The leader of the Invaders in 6.
- Disney Villain Death: Falls to his death before explodes in a massive explosion.
- Eye Beams: Purple ones that aim at you.
- Final Boss: Of 6.
- Flechette Storm: Has an attack where he charges energy then releases it in crescent projectiles. Then they fly at the player from the left and right, or may even converge on them from all directions.
- Hold the Line: The final part of the battle turns into a Free-Fall Fight where he is invulnerable, sending huge waves of destructible projectiles dowanwards at you.
- Large and in Charge: He is one of the biggest Invaders there.
- Spoiler Cover: The PS2 covers blatantly show the Invader King. Using its sprite, this makes the King into an Evil Overlooker in the process.
- Trick Boss: The heroes face off the pod where he is encased in. It stays there, doesn't do anything, and is periodically accompanied by the Invader Drones. When beaten, a bunch of Morden soldiers come in to celebrate with a victory music of sorts and suddenly, his eyes flash and destroy the soldiers.
- Debut: Metal Slug 4
A mysterious organization whose threat to the world was the release of the "White Baby Virus", a supervirus powerful enough to penetrate any mainframe's defenses. It also appeared as though Morden was supporting their efforts, though they had made a robotics plant at their base, creating several Morden bots, possibly including the one seen in the opening sequence.
The main man himself supposedly died at the end of the game when his base was destroyed, making him the first antagonist in the series to die for good. However, the credits sequence showed an intact computer broadcasting something...
- The Cracker: The Amadeus Syndicate are a team of cyber-terrorists.
- Elite Mooks: The disguised Amadeus troops use Heavy Machine Guns in the final level.
- Everyone Calls Him "Barkeep": The leader is referred as "Doctor" in Metal Slug Attack.
- Evil Old Folks: Amadeus himself.
- Framing the Guilty Party: Their soldiers dress up as Morden's troops, and they have robot Mordens and Allens, presumably to invoke this trope. In the last level, they instead dress up as Regular Army troops.
- Mecha-Mooks: Employ a lot of these.
- Palette Swap: In Attack, the Infantry are purple colored Rebel Soldiers.
- Robot Me: Robot Mordens and Allen O'Neils.
- Synthetic Plague: They managed to harness the Mummy and Zombie viruses from the previous games.
- Villain Team-Up: With the Rebel Army in Attack. When Allen and Abigail were being ambushed by the robots, they assumed the Syndicate betrayed them. They were not; it was the Syndicate's supervirus doing all the dirty work for her own.
- Debut: Metal Slug 3D
Pronounced Ogma, he is the head of the ridiculously massive company named after himself, Oguma was apparently funding Morden's efforts, but was actually using him to help find a recording device deep underground, the Alator. It turns out that Oguma was one of few survivors of a long-extinct race, the Tuaha de Dunan, who were shown to be technically advanced.
His culture was said to self-destruct at the peak of their evolution; to combat this, they placed a recording device on a planet, then hibernated for 300 million years. If the information gathered by the device clashes with them, they simply erase the world's history and start over, which has possibly caused some time-space problems.
Near the end of the game, after betraying Morden, he used the Alator to release the Lugas, which then absorbs the information from Alator and begins its mission to erase history, prompting the crew to stop it. When Lugas was absorbed by a previous experiment, the Luu (and beaten by the crew afterwards), it goes crazy as Oguma and his followers stay behind in an attempt to further stop it, despite Marco's protests.
At the game's end, as Rumi is about to head out, Oguma shows up out of nowhere and hands her his information disc before leaving, hoping the people would learn from his prior mistakes.
- Abusive Precursors: Oguma and his people essentially began life on Earth, but they have no problem snuffing it out in pursuit of their goals.
- Affably Evil: Speaks in a very polite and calm voice. When beaten, he admits his people's time has come and gives his data to Rumi, since humanity won out.
- Chuck Cunningham Syndrome: He is not present in Metal Slug Attack nor its predecessor.
- Shout-Out: The Tuaha de Dunan are named for the pantheon of Celtic Mythology. Lugus, their secret weapon, is named after a major god.
- The Starscream: Betrays Morden halfway through the game after showing his true colors, and eventually becomes the game's Big Bad.
- Debut: Metal Slug Attack
An expansion of the mummy enemies, the Pharaoh, Mummy Warrior, and Mummy Cat make their first appearance in the "Mummy" event.
Tropes for all three characters:
- Actually Four Mooks: Subverted. While the Pharaoh's Arc consists of multiple mummies on a chariot, they are all part of the same unit.
- Distracted by the Sexy: The Mummy Cats' main way of luring their enemies.
- Dub Name Change: The Mummy Cats are called Sexy Mummies in Japan.
- Enemy Summoner: The Mummy Cat's attack is to summon mummies that spit out poison bombs. If her third skill is unlocked, enemies hit by them have a chance to be stunned.
- Kill It with Fire: The Mummy Warrior uses a long torch as his weapon.
- Palette Swap: The Lovely Mummy is a red colored version of the Mummy Cat.
- Support Party Member: The Mummy Cat is awkward to use, but three of her four skills involve increasing the strength of Mummies, Mummy Warriors, and Mummy Dogs.
- Villainous Breakdown: The Pharaoh turns green in rage alongside his minions after being defeated. As the Tyrant Pharaoh, he starts commanding in a furious manner.
Support Characters and other notable NPC's
Rumi originally joined the Regular Army to make use of their medicinal facilities to help her ailing mother, who had a weak heart, and her sister Madoka, who was physically ill. Due to a paperwork SNAFU, she was shipped to the front lines, and despite having never completed her training, she made it back unscathed, a miracle in and of itself.
She was offered the chance to leave and live life as a civilian, but she declined the offer, and was soon transferred to the Supply Division. Before each mission, she fills her backpack with various supplies, and treks out to deliver the goods to Regular Army Soldiers... but there's one problem. She's horrible with directions, and is likely to wander off and be found in a completely different location, earning her the nickname "The Wandering Ghost" by most soldiers. She later found out her sister Madoka also joined to become more physically fit, and was also placed in the Supply Division... and shares the same atrocious sense of direction her sister has.
Though mostly a background character in the main games, Rumi was given a bigger role in Metal Slug 3D, giving information to Marco and even allowing access to a Garage where the player could customize their own Metal Slug vehicle.
Rumi and Madoka tropes:
- Action Girl:
- Promotional art for Metal Slug Defense shows Madoka parachuting while operating a bazooka. She is not a unit in Defense but she is in Attack, using her bazooka from her backpack and throwing a medicine item to heal units.
- Rumi turns into one in Metal Slug Attack. She throws grenades from her backpack to her foes and tosses support items to her allies. Madoka gets added later, packing a Bazooka with great range and a humongous rate of fire and healing the front line.
- Beware the Nice Ones: These two have some obscenely powerful Normal attacks in Attack.
- Butt-Monkey: A minor one, tagging either one of the sisters will cause them to fall to the floor and shooting them from the back tears their backpack open, dropping various items. The former also occurs when the player taps on Rumi on both tower defense games.
- Combat Medic: Madoka's special in Attack heals friendly troops.
- The Chick: Compared to Fio, Rumi is not willing to fight (and never wanted to do so in the first place), but Rumi is nice enough to help her fellow allies whenever she can.
- Cute Clumsy Girl: Given the above. It's taken even further in 3D when Rumi tries a dynamic entrance from a helicopter and screws it up.
- Fanservice Pack: Apparently, they've been starting to unbutton their shirts since Defense, even though their sprites in Attack show them with their shirts buttoned all the way up.
- Fingerpoke Of Doom: Rumi flails her hands like an angry toddler as her MSA melee attack. It does a lot of damage.
- In-Series Nickname: "The Wandering Ghost"
- It Runs in the Family: Both sisters being terrible with directions.
- The Medic: Rumi is seen in the bad ending of Metal Slug 4 taking care of the characters who got caught in the final mission's explosion. The Recovery Support in Metal Slug Attack represents her in a nurse outfit. She later turns into a Combat Medic in the 2.3.0 update. In the 2.5.0 update, Madoka is literally this, as her special attack heals the players units on the map.
- Motor Mouth: In 3D, Rumi is very talkative, impudent, and prone to going on tangents. She even sasses Marco after he gives her direct orders (she's a corporal; he far outranks her at Major), but she falls in line when he gets more direct.
- Mukokuseki: Let's be honest, they look even less Japanese than Eri.
- No Sense of Direction: Though they count as P.O.W.s, they are never caught by the enemy. They just happened to wander through the area.
- Older Than They Look: Despite being a Palette Swap, Madoka is eleven years older than Rumi.
- Out of Focus: Rumi has had more game appearances and cameos than Madoka. In both tower defense games, Rumi is the one who generates AP in the field and gets playable status in Attack. In Attack only, Madoka appears in the item support menu, but now appears as a playable unit alongside her sister in the 2.5.0 update.
- Palette Swap: Madoka has brown hair and grey attire compared to Rumi's blonde hair and green attire.
- Pint-Sized Powerhouse: Both walk and carry an overly large backpack holding various ammunition and food items. Downplayed as they seem to be struggling to keep balance.
- Series Continuity Error: Metal Slug 3D has Rumi ranked as a Corporal even though she's a Sergeant in every game she appears in.
- Stun Guns: Madoka's close range attack in Attack.
- Timed Mission: If they are on screen long enough without being tagged, they will stop to salute and run away, not giving any credit to the player for rescuing them.
- Unusually Uninteresting Sight: Both sisters tend to wander the active battlefield without any care. It is not until they see one of the protagonists where they bail out of there.
A Second Lieutenant of the Regular Army, he's a living legend among the soldiers. Pretending to be a captured POW, once he's "rescued" by the player, he helps out by firing homing Hadokens at the enemies and spin-kicking anyone else who gets too close. He will flee if you die, though.
Hyakutaro Ichimonji tropes:
- Guide Dang It!: Sometimes appears when the player hits a specific invisible spot multiple times.
- Kamehame Hadouken: His main attack has him fire a homing hadouken at enemies. It also deals pretty good damage too.
- Obfuscating Stupidity: He pretends to be a captured POW on purpose. Once he's "rescued", however...
- Screw This, I'm Outta Here!: Runs away once his rescuer dies.
- Shout-Out: His first name starts with the letter H, and his last name is Ichimonji, but he's no Hayato. Doesn't stop him from kicking ass though.
An Israeli orangutan that wears a diaper and carries an Uzi.
- Attention Deficit... Ooh, Shiny!: He's an animal, so don't expect him to be as focused on the mission as you are.
- Badass Normal: Compared to the main characters, who are unstoppable killers, he's just a monkey with a submachine gun. You still wanna mess with him?
Combat School Instructors
The drill instructor from Metal Slug 1 (Neo Geo CD and PSX).
- Ascended Extra: While every instructor in the series shows up in Metal Slug Defense, Sophia is the only one that hosts the Combat School in Attack (along with new sprites for her).
- Babies Ever After: Margaret, the instructor from Metal Slug X hints that Sophia retires to raise a family.
- The Bus Came Back: Shows up with Margaret in the second and third Pachislot games in Japan. In the West, it is in Metal Slug Defense.
- Ms. Fanservice: There's a good amount of art dedicated to her in the art galleries of the home versions.
- Passionate Sports Girl: What made her easily excel as a member of the Peregrine Falcons. Her favorite sport is Basketball, and also dabbles in bass fishing.
The drill instructor of Metal Slug X and Gimlet's mission control in Metal Slug: Second Mission.
- Ascended Extra: Unlike other instructors, she has given larger roles in certain games. In Second Mission, she appears as mission control in the main adventure and even shows up in certain missions as the end goal. In Defense, she hosts the game's events.
- Art Shift: Metal Slug Defense uses her sprites in X for the Events and her new artwork for the Combat School.
- Drill Sergeant Nasty: A jerk to you on the lower ranks, although she'll soften up as you rise among the ladder.
- Early Installment Character Design Difference: Wore a green military dress in X before changing to a blue dress for Second Mission onward.
- Easter Egg: Touching her breasts in Metal Slug Defense will cause her to react depending what rank you are in.
- Eyes Always Shut: If she opens them, you've either impressed her, or you've made a complete ass of yourself.
- Hair Color Dissonance: It's uncertain if her hair is blonde or lightish brown but sometimes her hair is represented by a darker shade of brown.
- Like a God to Me: Hitting the Super Devil rank will make her admire you to the point of calling you "Her Majesty".
One of the two drill instructors in Metal Slug 6.
One of the two drill instructors in Metal Slug 6.
- The Type-R, which sacrifices power for maneuverability.
- The Experimental, which sacrifices maneuverability for power.
- The Type-B, which is stronger in all areas, the Bronze, which is never used by the player.
- SV-000 and the Proto 2, a less defensive prototype that is able to turn around.
- The Black Hound, a Ptolemaic-made variation the is remotely controlled and equipped with a laser and homing missiles.
- MS-Alice, an SV-001 inhabited by a sentient A.I. named Alice; created by Marco.
- A.I. Is a Crapshoot:
- The Black Hound's an AI-controlled tank that goes rampant, attacking/killing its own Ptolemiac allies in the area before you face it.
- Averted with MS-Alice, who is completely loyal to Marco for creating her.
- Armored Coffins: There's no way to easily bail out of the 000. Either you get out after defeating all enemies or letting it explode.
- Armor-Piercing Attack: Any of them can acquire Armor Piercing Shells, which do extra damage against enemy tanks, and, most importantly, fly all the was across the screen and are spammable.
- All Your Powers Combined: The Type-B has the positive traits of the Experimental and the Type-R
- Backwards-Firing Gun: The SV-001 Type-R in the first level of the third game has the unique property of firing in the direction opposite the player points. This is important, since the first boss is spent frantically running away from it.
- Bonus Boss: Fighting the Black Hound is entirely optional in a secret area, and it gives no reward.
- Discard and Draw: As an enemy, the Black Hound is capable of ramming, firing its main cannon, a laser, a mortar attack, and its own machinegun. As a playable unit in Advance, it retains its capability to ram enemies and fire its main cannon, but lacks the laser, mortar and machinegun. Instead, it has the ability to spam homing missiles.
- Escape Pod: They are equipped with a floatation device, which is buoyant enough that the player can survive falling from space with it.
- Homing Projectile: The Black Hound uses this when it becomes playable in Advance. A rapid fire version of it, too.
- Mini-Boss: The Black Hound first appears as an optional boss in 5 before becoming playable in Advance.
- Mighty Glacier: They all take two to five hits to the player's one. However, their overall slower speed and lower jump height also makes dodging harder.
- Promoted to Playable: In Metal Slug Advance, finding the Black Hound's card will allow the player to use it. Unlike its encounter in 5, it primarily uses homing missile spam.
- Red Ones Go Faster: The Type-R is orange.
- Super Prototype: Ad advantage the 000 has over the 001 is the ability to turn around fairly easily. Unfortunately, the exit hatch is easily warped, making the thing into a deathtrap if it gets hit at all.
- Suicide Attack: Pressing Fire and Jump while in it will cause it to rush forward and explode.
- Action Bomb: The Fat Lizard ammo, used by the Walker Slugnoid and the Type-R, which is a small ball with legs that runs to the left of the player, then explodes.
- Breakable Weapons: It loses its cannons when damaged. After taking two hits, it's left without any vulcans.
- This Looks like a Job for Slugnoid: It's only ever really able to shine in situations that require more vertical movement than horizontal. In 2,, the fact that its missile travel downward means its only really useful when an enemy is directly below you. It appears to be designed with fighting the second boss of 2, its first appearance, in mind.
- Glass Cannon: While its firepower is stronger than the Slugnoid, it's very cumbersome to use, making it hard to keep it around. In comparison to other Slugs and the players it's still a mighty glacier.
- In a Single Bound: The Slugnoid's specialty, which is improved even more for the Slugnoid Type-B.
- Jump Jetpack: Its high jumps are jetpack-assisted.
- Molotov Cocktail: Certain versions of the Slugnoid have an incendiary bomb as their bomb ammo, setting the floor underneath on fire.
- More Dakka: It has two cannons as opposed to one.
- Nerf: X makes some levels harder by replacing the SV-001 with the more awkward Slugnoid.
- Phallic Weapon: Its cannon points straight down between the legs.
- Red Ones Go Faster: The Type-R, but it's still not as fast as even the SV-001 Experimental.
- Shows Damage: Taking damage causes the Slugnoid to lose a gun.
- Walking Tank: It's on two short, if stubby, legs.
- Automaton Camel: Averted in one instance. After the first level of 2 or X, it will neglect to follow the protagonist, to remain near a water source. Otherwise, it is incapable of being hurt.
- Denial of Diagonal Attack: While its cannon can fire in all directions, it can't turn around. So you will only be able to throw grenades forward while on it.
- Fragile Speedster: Faster than the other tanks, and faster than the player when runnning. However, outside of elevating the player above low-ground attacks, it offers no protection.
- Lovable Coward: It refuses to follow the protagonists into an ancient tomb, or into an army of man-eating plants, but is invincible when you do have it.
- Truth in Television: Camel-mounted machine guns actually existed in real life, called zamburaks.
- Weaponized Animal: A camel with a rapid-fire zamburak attached to its side.
Slug Flyer tropes
- Cool Plane: It's a hilariously small aircraft that functions just as well as a normal one, and comes with a rapid gun and missiles to boot. It can even carry an SV-001 on top of it without any hindrance in performance.
- David vs. Goliath: The fight between Slug Flyer (if you chose it) and the Dragon Nosuke has the Flyer smaller than the Dragon Nosuke's "head". The fight between Slug Flyer and Shooting Ray in 5 shows that the Flyer is barely the size of a single engine of the Shooting Ray.
- Homing Projectile: Its missiles orient themselves slightly on their own.
- Jet Pack: Starting in 3, many of them contain a jetpack and goggles for the player, for if the Flyer gets destroyed.
- This Looks Like a Job for Aquaman: It's usually only available when enemy planes are about, an exception being 2/X where it can be used against the Dragon Nosuke.
- Unexpected Shmup Level: Tends to appear in several Shoot 'em Up-like segments of the games.
Elephant Slug tropes
- Fire-Breathing Diner: To gain the ability to shoot fireballs, it must pick up a hot pepper.
- Lightning/Fire Juxtaposition: The two Mutually Exclusive Powerups that are unique to it are a hot pepper that gives it the ability to shoot fireballs, or a car battery that grants it the ability to shoot a lightning beam.
- Mighty Glacier: While it does not technically offer any protection, it is so tall that almost no zombies that are on the same floor as the player can hit them. Meanwhile, it can't jump is as slow as molasses.
- "Shaggy Dog" Story: It starts to help you after you free it from the ice its trapped in. In the end, the player either abandons it among the zombies or leaves it trapped in another pool of ice.
- Shock and Awe: It can breathe electricity if it eats a car battery.
- Trampled Underfoot: It can kill a zombie merely by walking over it.
- Weaponized Animal: An elephant with a gun attachment to it. It can even eat peppers or batteries for it to use fire or electrical attacks!
Slug Mariner tropes
- Cave Behind the Falls: One inexplicably holds two Mariners in the third stage of 3.
- Inertia Is a Cruel Mistress: It uses high-mass rounds, giving it serious difficulty when shooting from below
- Shout-Out: The Slug Sub is a direct recreation from the submarine from In the Hunt, while the Slug Mariner is essentially a chibi Thunderbird 4 from Thunderbirds.
- Super Prototype: The Slug Sub is actually the prototype of the Slug Mariner, despite its more diverse moveset.
- Denial of Diagonal Attack: While its cannon can fire in all directions, it can't turn around. So you will only be able to throw grenades forward while on it.
- Fragile Speedster: Faster than the other tanks, and faster than the player when runnning. However, outside of elevating the player above low-ground attacks, it offers no protection.
- Weaponized Animal: An ostrich with a rapid-fire gun attached to its side.
- Arm Cannon: It fires its equipped weaponry from them.
- Double Jump: It's capable of using a Jump Jet Pack if it jumps in midair.
- Exclusive Enemy Equipment: Averted, you're able to hijack them after killing their pilots.
- Hand Blast: It appears to fire its weaponry from its palms/claws.
- Jump Jetpack: Its double jump is jetpack-assisted.
- Mechanically Unusual Fighter: Out of all the slugs, its ammunition is limited and it can change its weapons depending on the ammo crates you pick up.
- Sniping the Cockpit: Their defeat animation as the rebel soldier within get killed. If you lack a slug, it'll become rideable, otherwise it explodes.
Bradley Slug tropes
- Cutscene Power to the Max: Jumping into it for the first times has the player turn the Bradley Slug around to face the correct direction, something that would be incredibly useful to do in game but is impossible for the player to do.
- Good Colors, Evil Colors: Bright Green to represent the Regular Army, as opposed to the grey/dark green of the bad guys.
- Glass Cannon: It houses one of the most powerful secondary fires available, but is very fragile.
- How Do I Shot Web?: Despite being found in the hands of rebels, they don't have any idea how to work its vulcan cannon or its jumping ability, only knowing how to operate its indirect missile fire like their standard Bradleys.
- Jump Jetpack: Is jumps with the help of a thruster beneath its treads.
- Mercy Invincibility: Subverted. It receives no invincibility and can even be hit multiple times with the same bullet.
- Ambidextrous Sprite: The Slug Gunner swaps its weapons while turning.
- Awesome, but Impractical: The LV Armor, unlike other slugs, requires ammo, can't shoot diagonally (some of them can do the heavy machine gun spreading motion), and takes one full second to jump makes it a liability at the worst of times.
- Close-Range Combatant: The Ptolemaic Claw Unit is the only Armor to not have any projectiles at all, only using its fists. Conversely, the MG has only guns and no ability to melee.
- Denial of Diagonal Attack: The LV Armor has a major deficiency in its ability to shoot diagonally, which even applies to heavy machine gun ammo.
- Double Jump: Most kinds can use rockets to boost itself once in the air.
- Gatling Good: One of the Slug Gunner's arm is equipped with a gatling gun.
- Mini-Mecha: They are mechs as large as the slug units.
- Transforming Mecha: The SVW-001 can morph between a Tank and a Mecha.
- Pile Bunker: The Slug Gunner has a pile bunker powered by revolving chamber.
- Super Prototype: For those who prefer speed over mobility, the Proto Gunner is actually better.
- Boss Arena Idiocy: Its Wave-Motion Gun attack would be much more accurate if there were any platforms for the target to stand on.
- Cool Plane: Albeit one that doesn't fly.
- Stationary Boss: Doesn't move from its spot, due to having crash-landed and made into a stationary base of operations.
- Warm-Up Boss: All its attacks are relatively easy to avoid.
- Wave-Motion Gun: It can charge up with one of these and fire. Either crouch or stay on higher ground to avoid it.
- Boss Arena Idiocy: Of all the places it could fight you in, there just had to be three rising platforms that gave you ample cover from most of its attacks.
- Cool Plane: Unlike the Tetsuyuki, this one does fly.
- Recurring Boss: It also appears in Metal Slug 3 as one of the minibosses in the final level. Allen pilots it this time.
- Traintop Battle: Its encounter in Metal Slug 1 has you battle it on a moving train.
- Villain: Exit, Stage Left: In Metal Slug 1, Morden's in the aircraft. When destroyed, he drops out of it, but a Rebel in a Flying Tara rescues him and exits the area.
- Land Mine Goes "Click!": Its side launchers can fire landmines.
- Meaningful Name: Tani Oh means Valley King in Japanese. Appropriately enough you encounter it at the top of a valley.
- Samus Is a Girl: Not the tank itself, but its pilot. In the Metal Slug pachinko game, it is revealed that its pilot is a blonde woman named Letta.
- Tank Goodness: A huge Rebel army tank with a laser cannon/railgun type weapon and mine launchers.
- Wave-Motion Gun: The main cannons fire some sort of laser or railgun type weapon that hits anything in its range instantly.
- Degraded Boss: After fighting them as a boss, the following level has you fight a miniboss version of Shoe as it advances towards you from behind. You also have to fight Shoe as a miniboss in Mission 5 of X.
- Dual Boss: You fight both of them at the same time.
- Mini-Boss: Shoe is encountered as one in Mission 5 of both the original game and X.
- Tank Goodness: Two large Rebel army tanks with fireball cannons and missile launchers.
- Fire-Breathing Weapon: Carries a hidden flamethrower on its bottom.
- Macross Missile Massacre: Its carries a multi-missile turret on top.
- Recurring Boss: Appears as the first boss of Metal Slug X.
- Tank Goodness: Carries a Girida-O tank on its back to serve as its rear firepower.
- Weaponized Car: It is a weaponized armored truck.
- Degraded Boss: It reappears as one of the many Mini Bosses of the final mission of 3, literally just as the Mars People make themselves known again (a Martian masquerading as Morden during the fight itself). It is fought in almost the exact same way, except the player has access to a mounted machine gun to make it even easier.
- Destructible Projectiles: Both its bombs and missiles can be destroyed. A very good thing too, since it would be nearly impossible to avoid some of its attacks otherwise.
- Death from Above: It's capable of using a carpet bombing attack where it drops bombs all over the area.
- Final Boss: The last battle of Metal Slug 1, where Donald Morden himself pilots this.
- Homing Projectile: Its missile attack will home in on the player.
- Macross Missile Massacre: Has a missile launcher on its front that shoots a swarm of homing missiles.
Metal Slug 2/X
- Demoted to Extra: In Metal Slug X, it is replaced by the Iron Nokana as the first boss, and is instead relegated to the miniboss of the third mission.
- Car Fu: In Metal Slug X, it drops tanks on you as an attack.
- Cool Plane: A large gunship with anti-air guns and can carry troops.
- Clown Car Base: In Metal Slug X, it can carry an unlimited number of tanks on its wings, and replenishes them after it drops them.
- Flunky Boss: In 2, it will spawn Arab soldiers to attack you. Subverted by the bazooka soldiers that assist it once its health gets low, they cannot be damaged in any way.
- Recurring Boss: It appears as a miniboss in Metal Slug X.
- Tank Goodness: It is capable of carrying tanks on its wings, and they do attack with their cannons.
- Weaponized Exhaust: One of its more dangerous attacks is to fire hot exhaust from its jet engines, then sweep the area by moving left and right.
- Astonishingly Appropriate Appearance: It is an excavating machine that happens to resemble a cobra and also happens to be fought in an ancient Egyptian pyramid. Cobras were one of the animals worshiped by the ancient Egyptians.
- Mechanical Monster: A giant excavator resembling a cobra that tries to "swallow" the pillar you're on.
- Macross Missile Massacre: Can fire out a slew of homing missiles.
- Platform Battle: The player has to jump from platform to platform as it chases them up the large pillar.
- Reptiles Are Abhorrent: A giant cobra excavator mech that's hell-bent on "eating" the player characters.
- Rise to the Challenge: It'll charge upwards now and then, and as such the player needs to move upwards as well to avoid electrical death.
- Wave-Motion Gun: It is equipped with a laser cannon in its mouth. While it is originally used for tunnelling through hard layer of rock, it can be also used for combat.
- Fire-Breathing Weapon: Its underside carries a flamethrower.
- Flunky Boss: The tank is capable of spawning helicopter firebombs that home in on you and can be destroyed.
- Gatling Good: Comes equipped with a gatling gun that can fire either small or large bullets.
- Ground Pound: If the player tries to be sneaky by hiding under its legs to avoid its gunfire, it will "sit down" on the platform and crush them instead.
- One-Hit Kill: Getting crushed by it will destroy your Slug and you instantly.
- Spider Tank: A tank with four "legs" that allow it to walk or crouch.
- Background Boss: It attacks the player from the background, never once entering the foreground or the same plane as the player.
- BFG: Once its health gets low enough, it'll open up and reveal a HUGE cannon that fires large exploding bullets. This is incidentally also its weakpoint.
- Military Mashup Machine: It is essentially a land battleship on tank treads.
- Rocket Jump: Surprisingly, you can use the explosions from its BFG to boost yourself and get a better shot at it.
- Tactical Suicide Boss: If it didn't open itself up to expose its huge cannon, it would be functionally invincible.
- Tank Goodness: A cross between a battleship and a tank.
- Abandon Ship: When defeated, Rebel soldiers can be seen jumping out of it and into the sewer water.
- Down the Drain: The Hozmi is fought in a sewer, for some reason.
- Expy: Of Tani Oh, being equipped with a laser cannon-like weapon and the player has to shoot it from below.
- Shock and Awe: The main turret has an electrical cannon that fires an electrical laser, while it also fires electrical spheres at you.
- Shows Damage: The sections of its body appear to become increasingly damaged as you fire at those specific sections.
- Wave-Motion Gun: The main turret fires an electrical laser not unlike Tani Oh's cannon.
- Bait-and-Switch Boss: Morden prepares to engage you in a new craft before the Dai-Manji blows it to bits and kidnaps Morden, beginning the actual fight.
- Combining Mecha: Once beaten, the Rugname appears and the Dai-Manji attaches to its bottom hull, becoming the main weapon.
- Degraded Boss: In Metal Slug 3, you have to fight them as Giant Mook enemies in the final stage.
- Death from Above: Has a carpet bombing like attack similar to the Hi-Do, except this one fires indestructible energy bolts.
- Flunky Boss: Constantly spawns Mars People in flying saucers to harass the player characters.
- Meaningful Background Event: As soon as the Dai-Manji engages you, an aerial dogfight ensues between the Rebels and the Martians in the background. This continues on until the Rugname is destroyed.
- Shock and Awe: Attacks with an aimed electrical laser attack.
- Flunky Boss: Constantly spawns Mars People in flying saucers to harass the player characters.
- Mini-Boss: In Metal Slug 3, you have to fight it as a miniboss in the final stage.
- Sequential Boss: Fought immediately after the Dai-Manji is destroyed, with the latter attaching itself to Rugname's body, becoming its core and main weapon.
- Shock and Awe: Attacks with an aimed electrical laser attack from its Dai-Manji attachment.
- Shout-Out: The way it's defeated in Metal Slug 2/X is obviously a shout out to Independence Day, where an aircraft crashes into a weakspot.
- Wave-Motion Gun: It is capable of firing a huge laser cannon below it.
Metal Slug 3
- Advancing Boss of Doom: It constantly advances towards the player characters, forcing them to keep moving or get crushed by it or fall into the water.
- BFG: Once it Turns Red, the tank opens up and reveals a huge cannon that fires large bombs to destroy the terrain.
- Bread, Eggs, Breaded Eggs: The first mission itself has you fight either the Rebels or giant crabs in two separate paths. Both concepts converge with the Huge Hermit battle.
- Fireballs: What the tank shoots at you in its first phase.
- Giant Enemy Crab: An enormous hermit crab with a tank as its shell.
- Stealth Pun: It has a huge tank in place of a shell. In other words, it's a tank shell.
- Tank Goodness: It carries an enormous tank on its back in place of a shell.
- Weaponized Animal: A huge hermit crab with an enormous tank for its shell.
- Warm-Up Boss: Its attacks are relatively easy to avoid, and you even get a Metal Slug or a Slugnoid at the start of the battle to assist you. It becomes even easier once it stops using the fireballs and starts using the large cannon.
- Abnormal Ammo: The Monoeye UFO attacks by dropping monoliths on the player characters.
- Crosshair Aware: It targets a player with a green laser before dropping a monolith on them.
- Cyclops: The Monoeye aliens that protect it all have a single eye.
- Death from Above: Its sole attack is to drop monoliths from above that slowly sink into the ground and also act as obstacles.
- Eye Beams: The Monoeye aliens attack by firing fireball like projectiles from their eyes.
- Hoist by His Own Petard: Using the zombie blood vomit can deal incredible damage to the Monoeyes and the Monoeye UFO. This is only usable if the player gets zombified...by the very virus the Monoeye UFO spread around. In fact, certain versions of the game even give you an achievement for beating them as a Zombie.
- The Monolith: Drops monoliths with alien inscriptions on the player characters. They act as obstacles that remove themselves over time as they sink into the ground (faster if shot at).His
- Sequential Boss: After fighting the Mini-Boss Monoeyes, did the artifact come to life and start attacking on its own.
- Turns Red: When its health gets low, it starts glowing orange instead of green, and it drops monoliths at a faster rate.
- The Virus: The mononith is responsible for creating the virus that turned the people in the level into zombies.
- When All You Have Is a Hammer...: Unique for the series, both the Monoeyes and their UFO itself have only one attack apiece.
- Wolfpack Boss: The first phase has six to eight Monoeyes appear and float around the structure, and coordinate their eye beam attacks. Thankfully they're not too durable.
- Zombie Apocalypse: It is the cause of the zombie outbreak that has infected several people in the level and possibly the player.
- Attack Its Weak Point: It is only vulnerable in the head.
- Eye Beams: It is capable of sweeping a great area with electrical eye beams.
- Fireballs: Every time it smashes the giant rocket on the ground, it'll explode into a slew of fireballs that rain down.
- Hammerspace: Capable of horizontally drawing a missile longer than the body from which it is stored, multiple times.
- Homing Projectile: The missiles it fires out will home in on the player characters.
- Improbable Weapon User: One of its "attacks" has it grab a giant missile and smash it into the platform, destroying that part of the platform and causing fireballs to rain down from the explosion.
- Killer Robot: A gigantic and weaponized toy robot.
- Macross Missile Massacre: In place of its left arm is a multi-missile launcher that fires destructible homing missiles.
- Shock and Awe: Getting hit by its eye beams will electrocute the player character.
- Attack Its Weak Point: Its only vulnerable in its rather small Power Crystal on its forehead.
- Cruel and Unusual Death: Getting hit by its Wave-Motion Gun will turn the player character into a rain of coins.
- Power Crystal: This serves as its weakpoint and also allows it to fire its Flechette Storm attack.
- Flechette Storm: Fires spiked projectiles of light from its crystal. Yellow ones are aimed at random while red ones are aimed at the player characters.
- Meaningful Name: Sol Dae Rokker is a play on "Sol De Roca", which means "Sun made of rock" in Spanish.
- Shaping Your Attacks: One of its attacks consists of summoning ghostly energy wolves that act as explosive projectiles.
- Turns Red: In both the literal and trope sense. It'll start turning red as it takes damage, and its attacks will also become faster.
- Wave-Motion Gun: It is capable of firing one from its "mouth". Getting hit by it will turn the player into coins.
- Lone Wolf Boss: It isn't associated with any enemy faction at all.
Metal Slug 4
- Background Boss: It assists the Sea Satan by firing missiles at you from the background, despite being heavily damaged from the previous battle.
- Cool Airship: A huge airship constructed by both the Rebels and Amadeus Syndicate, and carries a plethora of weaponry.
- Sequential Boss: You have to fight its dorsal section, then its rear half of the gondola, then its front half of the gondola in three separate phases.
- Hoist by His Own Petard: Using the zombie blood vomit can deal incredible damage to it. This is only usable if the player gets zombified by the zombie virus bubbles it drops.
- The Virus: It releases bubbles filled with the zombie virus.
- Zombie Apocalypse: It is the cause of the zombie virus that has infected several people in the level and possibly the player.
- Gatling Good: Carries a gatling gun that will fire at the player if they're on top of it.
- Background Boss: The computer's final form is situated in the background.
- Beam Spam: The final form loves its lasers.
- Load-Bearing Boss: The game is not over once it defeated, you still have to escape the exploding base.
- Sequential Boss: You have to fight the Type α Mother Computer, followed by the Type β Mother Computer, and then the main boss.
- Stationary Boss: All three forms.
Metal Slug 5
- David vs. Goliath: You can bring a Metal Slug to battle against it where your Slug will be the David and Metal Rear will be the Goliath.
- Evil Knockoff: A gigantic knockoff of the SV-001 created by the Ptolemiac Army after they stole the Metal Slug's blueprints.
- Fireballs: Its main cannon fires large but slow moving fireballs out.
- Gatling Good: It is armed a gatling gun in the same spot that the Metal Slug has a machine gun in.
- One-Hit Kill: Getting crushed by it will instantly destroy the slug you're in, as well as you.
- Shout-Out: Its name may be a reference to Metal Gear.
- Tank Goodness: It is essentially a huge version of the Metal Slug that you ride, and comes with all the dangerous weaponry too.
- Bullet Hell: One of its attacks consists of firing a storm of flak shots forwards, when then drift back towards you in a hard-to-avoid field of bullets.
- Cool Plane: A gigantic aircraft used by the Ptolemiac Army.
- David vs. Goliath: You can bring the Slug Flyer to battle against it, where your Slug will be the David and the far larger Shooting Ray will be the Goliath.
- Flunky Boss: It is capable of spawning helicopter firebombs that home in on you and can be destroyed.
- Weaponized Exhaust: One attack used by its rear section has it try to torch the player characters with its exhaust.
- Exactly What It Says on the Tin: It's a machine that crawls on building walls.
- Flunky Boss: Every now and then, the commander will pop out and summon two Ptolemiac soldiers to attack you.
- Homing Projectile: It's capable of using a homing missile launcher that fires destructible missiles.
- Glass-Shattering Sound: Uses a sonic cannon to demolish the current floor you're on.
- Spider Tank: A vertical version, but loosely based on an arachnid nonetheless.
- Wall Crawl: Like its name suggests, it's fought at the side of a building where it crawls on.
Metal Slug 6
- Deadly Disc: Capable of launching a huge saw disc that advances towards you.
- Death from Above: One of its attacks causes stalactites to fall from the ceiling.
- Dishing Out Dirt: It is capable of firing boulders at the player. During the second phase of the fight it can also use its drill to cause stalactites to rain down on the player.
- Military Mashup Machine: A cross between an excavator and a drilling machine.
- This Is a Drill: It is capable of using its excavator drill to make rocks land on the area, and to attack.
- Death from Above: One of its attacks has it launch a huge rocket into the air that will then crash into the ground and cause a fiery shockwave.
- Hammerspace: Much like the King Jupiter, it can fire missiles larger and especially longer than the vehicle itself.
- Interesting Situation Duel: You fight on the side of this thing as it slides down a hill.
- Macross Missile Massacre: Most of its attacks consist of launching several rockets in various patterns at you.
- Advancing Boss of Doom: It'll advance in on the player when it's moving, forcing you to keep moving backwards.
- Berserk Button: Bait it into using its melee attack too often or take too long to defeat it and it will keep swinging its arms while moving, limiting your safe space. You'll know it's pissed when it does an angry stomping motion.
- Brain in a Jar: Its head appears to have a huge alien brain within that controls the robot.
- Car Fu: One of its attacks consists of grabbing a wrecked truck from the sewage and tossing it at you.
- Energy Ball: Its brain fires these out forwards, which then stop before aiming and flying at the player characters.
- Killer Robot: It's an alien Brain in a Jar robot that's hell-bent on chasing and killing you.
- Shock and Awe: It's capable of shocking the entire floor with electricity. To avoid this, you need to stand on one of those boxes that appear in the arena. It can also fire homing electric orbs at the player.
- Attack Its Weak Point: Its head is the primary weakspot.
- Sand Worm: A sea variant instead. It also acts as a Segmented Serpent. Metal Slug Attack would instead play this trope straight as it emerges from under the sand.
- Super Spit: It's capable of spitting purple acid at the player characters or even spewing a huge stream of deadly microorganisms.
Metal Slug 7/XX
- Background Boss: In its first encounter, it attacks you from the background, to the point where only its hands are attackable. You need to shoot the rocket minecarts so they'll launch a missile in the air that will hit it.
- Boss Arena Idiocy: Minecarts carrying rockets will constantly spawn at the bottom of the area, and shooting them will cause them to launch a missile at Crablops for huge damage.
- Cyber Cyclops: Like its name suggests, it has a single mechanical eye.
- Detachment Combat: The second battle against it reveals that it can detach its head and torso from its legs, and both are fought as separate enemies.
- Dishing Out Dirt: Both encounters with it has it capable of grabbing a stalactite from the cave ceiling and dropping it on you.
- Dual Boss: In Mission 3, its head and arms detaches from its body and you have to fight both of them.
- Eye Beams: It attacks you with these in its first encounter.
- Flunky Boss: Capable of deploying containers that spawn mole drones to attack you. The second time it's fought, it also drops exploding maggots and rebel soldiers.
- Giant Enemy Crab: It's a crab-like mecha with the capability of splitting into two, and also has a lot of firepower.
- Interesting Situation Duel: Partway through the second encounter, you'll board a diagonal platform lift. Once one of the halves is down, the other will attack you more relentlessly as the lift ascends.
- Macross Missile Massacre: It has a multi-homing missile launcher on its head, which it'll use in its first encounter.
- Meaningful Name: It's a crab-like robot. It has one eye. Hence, it's a crab cyclops.
- Not Quite Dead: When defeated in Mission 2, it's seen relatively intact, if powered down. Sure enough, it returns as the boss of Mission 3.
- Puzzle Boss: In its first encounter, you can only attack its arms. In order to do good damage to it, you need to shoot the conveniently-placed rocket carrying minecarts so they'll launch a missile into the air that will hit its body.
- Recurring Boss: It's fought as both the second and third boss of the game, except in different situations.
- Weaponized Exhaust: Its bottom half is capable of using an exhaust cannon during the second time it's fought, once the top half is destroyed.
- Ambiguous Situation: It's left ambiguous if it's truly destroyed since it doesn't explode when defeated, instead using a Wave-Motion Gun to propel the player characters up to the level endpoint.
- Flunky Boss: It will often summon two turrets on the waterfall face that fire various types of attack at you.
- In Case of Boss Fight, Break Glass: Its weakpoint is the glass-looking case in its middle, once its head armor is destroyed.
- Interesting Situation Duel: You fight it as it climbs up a waterfall, and the platforms you stand on is the boss itself and its arms.
- Killer Gorilla: A mecha that appears to resemble a gorilla in terms of body shape.
- Wave-Motion Gun: Once its top armor is blown off, it becomes capable of firing one out down the middle. It also uses one upon defeat, although this doesn't hurt you and instead propels you to the level endpoint.
- Attack Its Weak Point: They're only vulnerable in the bright red cores on each of them.
- Boss Arena Idiocy: If the head tank didn't have a convenient platform at its base for the player to stand on, it would be far more difficult to hit the Slave Tank. Likewise, if it didn't have a convenient area to stand on right in front of its weakpoint, it would be a lot more tricky to hit.
- Combining Mecha: The three of them can combine together into a larger form. While they aren't quite threatening in this form, they can crush any player characters between any of the parts when they do so.
- Death from Above: The Slave Tank is capable of firing several bombs into the air that rain on the player.
- Flunky Boss: The VTOL can summon elemental pod enemies to attack the player.
- Gatling Good: The VTOL has a gatling gun attachment on its front side.
- I Can Still Fight!: Destroying the core on one of them does not take it out of the battle, and it can still attack and move like normal. The fight's only over once all three lose their cores.
- In Case of Boss Fight, Break Glass: Their weakpoints appear to be red glass-looking cores.
- Interesting Situation Duel: The entire fight takes place on the three of them, where your player character uses them as makeshift platforms.
- Killed Offscreen: When all three are defeated, your character leaps off as the trio move offscreen. After some explosion sounds and screen shaking, their wreckage then flies back on-screen from the right.
- Meaningful Name: The trio is collectively known as the Union, can combine with each other, and all three of them need to be destroyed to defeat them.
- Shout-Out: Being made of three different parts with an odd core-looking weakpoint in each of them, it's a reference to the fifth boss of RType.
- Wolfpack Boss: You fight all three of them at the same time.
- Duel Boss: The boss battle consists of the player's Slug Gigant versus Allen O'Neil's Rebel Gigant, with no flunkies between you and him. If your Slug Gigant's health goes down, you automatically die and respawn as another cockpit for the Slug Gigant.
- Evil Counterpart: It's essentially a rebel army version of the Slug Gigant.
- Humongous Mecha: It's far larger than most of the pilotable mechs in the series.
- Macross Missile Massacre: It's equipped with a multi-homing missile launcher on its shoulder and Allen won't hesitate to spam it.
- Mirror Boss: You face it when piloting your Slug Gigant. In fact, if your Slug gets destroyed, you die and you'll respawn with another Slug Gigant.
- Battle Amongst the Flames: You face it at a lava field with floating scrap metal.
- BFG The main unit comes equipped with a huge cannon that destroys the scrap metal platforms on the lava.
- Boss Arena Urgency: Subverted, both Kraken and its tentacles can destroy the metal scraps you're on, only for more scrap to show up to replace them.
- Combat Tentacles: Eight of them, no less, and all of them are capable of using their own attacks. You need to destroy each individual one before the main head attacks you.
- Death from Above: The main unit capable of raining fireballs onto you or dropping cylinder grenades from above.
- Foreshadowing: It can be briefly seen emerging from the Future Army's portal as it gets destroyed.
- Gameplay and Story Segregation: It's capable of travelling under the lava, yet the Flame Shot will still damage it despite being less hot. Granted, you don't get the Flame Shot during the battle itself.
- Marathon Boss: The fight is separated into five phases, the first four involve destroying two of its eight tentacles, and the last being an attack on the main machine itself. Each tentacle has a good bit of health to complicate things.
- Sequential Boss: The first phases involve attacking and destroying its tentacles, before you can actually fight the main unit.
- Shout-Out: Its design appears to be like that of the Trumpet Lillies from In the Hunt.