Alongside the returning Peregrine Falcons Squad and S.P.A.R.R.O.W.S, a new subgroup called the Metal Device Project is introduced. Mainly, the M.D.P. focuses in developing a Powered Armor called the "Metal Device" for the next generation of soldiers, although they also create new Slugs.
Main Army Affiliates
An A.I. made sentient due to a programming error from Marco. Alice controls and inhabits an SV-001 and is able to produce a mass hologram of herself.
- Action Duo: Eventually became one with Marco in the form of Equippable Ally, who's able to utilise Alice's full potential.
- Attack! Attack... Retreat! Retreat!: Her "close range attack" is her running away with her Metal Slug in reverse. In her Extra Ops debut, she pulls this when she couldn't put a dent on Crablops and was about to be swarmed by the mutated crabs. Can also be a Tactical Withdrawal since it allows her to use her long range attacks again, especially when the enemy is distracted by units in front of her after retreating.
- Become a Real Boy: During the Halloween Another Story, she chose to work with Aswang for the possibility of gaining a flesh-and-blood body, for the purpose of being able to interact with her creator on a physical plane.
- Calling Your Attacks: Blows on a whistle during regular attacks and shouts into a megaphone during her Special.
- Cute Monster Girl:
- Her "Halloween Alice" variant. Operating a new timed firing program changes her appearance into a more fanservice-y, midriff-bearing Succubi. Said to be a prank by the creator of said firing program.
- Her "Everlasting Summer Alice" variant, again a prank by a programmer who couldn't get any vacation days. She's now a mermaid wearing a Seashell Bra.
- Determinator: A variant unit has her SV-001 nearly totaled and stripped of weapons, but she still fights on, directing other (empty)Slug units to make kamikaze attacks on the enemy.
- 11th-Hour Superpower: One of the last units released for Attack was the powerful SV-002 Metal Slug mk.2, controlled together by Alice and Marco.
- Fun with Acronyms: Alice's name packs in a couple of puns.
- The M.S. at the front of Alice's name is both an abbreviation of Metal Slug, it's also a riff on the title Ms., making her Ms. Alice.
- Abbreviate her whole name and you get M.S.A., which is also the acronym of the title of her game of origin, Metal Slug Attack.
- Instant A.I.: Just Add Water!: Alice was born when Marco made "a computer mistake".
- Marilyn Maneuver: When using a special attack, she moves upwards while her Slug leaps to fire a series of cannons. She holds her skirt down when she descends to normal height.
- Military Salute: Makes a tearful one as she's dying.
- Narrative Profanity Filter: It's less "profanity" and more "anything inappropriate". Marco being the Papa Wolf, programmed a filter or a content regulator into her that prevents her from thinking about anything seductive or sexual. Which makes her interaction with Vatn a little bit awkward.
- Taking You with Me: Tosses her destroyed Slug to the opposing army.
- Undying Loyalty: Towards her creator, Marco. Even as far as to hurl herself at an attack that was meant to kill him.
- Victory Pose: Shares the same one as Marco.
A soldier of the Regular Army. She was selected from the army to assist the Ikari Warriors.
- Kick Chick: Her close range attack is a crouched kick.
- Ascended Fanboy: She is very enthusiastic to work with the team she admires.
- Palette Swap: Of Tyra Elson.
A weapons engineer of the Regular Army, also part of the Sparrows division.
- All There in the Manual: Her last name is revealed in her concept art.
- Child Soldiers: Her age isn't given, but she's certainly young enough that both Marco and Eri are very uncomfortable with actually sending her into a battle, even though circumstances necessitated it. Eventually, the Regular Army members deemed Midori to be old enough to fight by herself.
- Conveniently an Orphan: Her parents died from a war. Her and Special Eri (also an orphan) both make the "Not Alone" team.
- Expy: To Navel from the pachinko version of Metal Slug 3. Both are young, pink-haired soldiers who fight using mechs and supports with the main cast.
- Extendo Boxing Glove: One of her close range attacks is a glove coming from her bag of tools.
- Palette Swap: Her Tetsujin Kun weapons, which are brightly colored Slug Armors.
- Rose-Haired Sweetie: Takes the battlefield in a far less serious matter than any other soldier.
- Sixth Ranger: Unofficially the fifth member of the main heroes (Marco, Eri, Tarma, and Fio).
A battle office lady from the future. She aids the Regular Army after accidentally landing on their base.
- Energy Weapon: Her laser gun.
- The Rival: To Nova.
- Stripperific: Is able to reduce her suit to a bikini in her victory animation.
A PF squad recruit who joined the Regular Army around same time as Roberto Nicola.
- Apologetic Attacker: In her Extra Ops event "Top Prospect", she apologizes to the Amadeus Morden Robot before she finishes it off. Not that the robot needed to be finished off.
- Berserk Button: Hates to be referred as a country girl, given as she lived there without public utilities for 18 years.
- Cute Bruiser: Gives off this vibe as well as dorky tendencies.
- Dodge the Bullet: Roberto says she's able to dodge bullets during training. Becomes Gameplay and Story Integration where Rita actually has a skill that allows her to dodge projectiles from enemy units.
- The Fashionista: Unlike her fellow teammates who wear standard military attire, she dresses in latest girly fashion trends.
- Flag Bikini: Her Everlasting Summer outfit.
- Kick Chick: Rita is apparently useless with a firearm but she excels in her physical training. According to Tyra, she could destroy a tank's cannon just by kicking, and that's before she was given special leg armor made by Midori. Not to mention she only uses her left leg in combat.
- Let's Get Dangerous! / I Am Not Left-Handed: Her special attack begins by warping a second leg armor onto her right leg and perform a Hurricane Kick.
- Red Baron: Earned the nickname "Wild Child on the Battlefield", though she wouldn't call herself a "wild child".
- Rememberthe New Girl: She joined the Regular Army around the same time as Roberto, even though Roberto's debut dates back to Metal Slug Mobile 4 in 2008.
- Took a Level in Badass: Before joining the Peregrine Falcons, Rita was from a rural area of Japan.
A lone wolf pilot who drives a modified Slug Gunner. Joined the Regular Army at Marco's request.
- Navel-Deep Neckline: Although not as low as Veronica's, the zipper ends just below her bosom.
- No-Sell: Her Gunner cannot be damaged while in tank mode.
- Pile Bunker: Longer than the standard Gunner. Her special attack gives it an explosive effect.
- Regenerating Health: Recovers part of her health every five seconds.
- Sugar-and-Ice Personality: According to Roberto, her cold personality is due to her not being accustomed to making conversations. She gets friendly once they get to know her.
- Transforming Mecha: Her Slug Gunner opens up and starts attacking when near enemies.
A female officer with strong leadership skills, takes command of a modified Di-Cokka tank with enhanced firepower.
- Calling Your Attacks: Does this with a swing of her baton before firing. Her special attack even has a Beat before she does this.
- The Enemy Weapons Are Better: A Regular Army officer who commands a modified Di-Cokka tank that's usually a Rebel Army vehicle.
- Expy: Her appearance and being in a tank may give the impression of Anchovy from Girls und Panzer.
- Guns Akimbo: Instead of a single cannon, Nikita's Di-Cokka has two.
- Just a Kid: Sort of a Berserk Button as she dislikes being treated as such. Practically her motivation to rise up the ranks so she can treated seriously.
- Law of Inverse Recoil: Nikita is often rocked back and forth every time her tank fires a shot.
- Magic Skirt: Averted, when she manages a win she does a cartwheeling flip out of her tank where her miniskirt betrays her modesty briefly.
- Non-Idle Rich: It's noted that she comes from a famous family and has many connections but refuses to rely on them, preferring to put in the effort herself.
- One-Steve Limit: Shares the same name as one of the playable characters in Metal Slug Revolution.
- Screw This, I'm Outta Here: Calls a Regular Helicopter to save her. Her ditched Di-Cokka is then sent careening towards the enemy forces.
- Small Girl, Big Gun: Downplayed. Her stature is small but her Di-Cokka tank is the size of a Metal Slug, that is equipped with a Wave-Motion Gun.
- Tank Goodness: Rides a modified Di-Cokka tank.
- Up Through the Ranks: It's stated that due to her skills, she's able to rapidly do this to the point where the top brass have trouble keeping up with her speedy and flexible tactics.
- Wave-Motion Gun: Her Solenoid Cannon special attack, that can be described as a smaller and faster version of Tani Oh's Andro Cannon.
- Weapon for Intimidation: Holds a baton (with a bow on it) to make herself more serious.
A member of the famed and talented Bradford family. She attacks with various weapons stored inside her robes.
- Parasol of Prettiness: With a shotgun acting as the handle. It also works as a shield.
- Short-Range Shotgun: Unless she uses her special, in which the damage given travels way farther than the animation shows.
- Taking You with Me: Runs towards her enemies with a dynamite on hand.
- Trenchcoat Warfare: Carries a landmine, a bomb, a Gatling gun, and a bazooka. She attacks in the respective order.
- The Rival: To Fio, due to Reika's family often being compared to hers.
A member of Sparrows.
- Evil Counterpart: Inverted. Her E.G.G.s are based on Abigail's laser drones.
- The Quiet One: Speaks in a slow manner.
- Shock and Awe: The E.G.G.s give out shocks of electricity and, when thrown together, produces lighting strikes. It can also stun enemies.
A scout member of the Regular Army. Is in a long search for her missing beloved Bersek.
- Death from Above: Her special is calling a group of Slug Flyers to air strike the opponent.
- I Will Find You: The closest she gets on finding Bersek is a destroyed ship; she immediately knows that he would cause that type of damage. Reika stops Louise from going further due to signs of an Invader close to him.
- Smoke Out: Tosses a smoke bomb before running away a few yards.
An AI created by Marco and Alice's sister. Heart operates the TS-001 Tandem Slug.
- Development Gag: The Tandem Slug resembles an unused concept of giant, futuristic, humanoid mechs holding guns◊.
- Emotionless Girl: Originally one, until White Baby hacked her and gave Heart self-awareness.
- Hologram: Flashes green just like her sister.
- Rocket Punch. Her special has the Tandem Slug dashing forward grinding enemies with its fist before ending in an explosion that deals massive damage. Its punch can also instantly blow up your base.
- Undying Loyalty: Earns an attachment to Tarma much to his confusion.
A soldier with impressive flying skills. She pilots a personalized Slug Flyer.
- Animal Motifs: Birds. Her shirt has a picture of bird on it.
- Energy Weapon: Her laser either go into multiple directions or drag along the ground.
- Gatling Good: Her Slug Flyer has a Gatling gun that fires out missiles.
Rita's cousin who has a love for justice.
- Boxing Battler: Unlike Rita, who uses kicks, Rocky fights with punching or uppercutting.
- Dismissing a Compliment: Hates being flattered and retaliates by punching them.
- Dynamic Entry: Rocky instantly deploys to the enemy lines from above and drops a large rocket on their heads.
- Instant Armor: Whenever Rocky punches the ground, she instantly wears a bodysuit for a brief moment before it disappears.
- Punched Across the Room: Punches Roberto and Tarma after they compliment her.
- Wearing a Flag on Your Head: Her special variant has a U.S. flag motif.
A young soldier who fights with his tiger guardian.
- Attack Animal: His tiger is equipped with various military weapons. It is somehow able to use them by itself.
- Conveniently an Orphan: Apparently the only survivor from a shipwreck when he was young.
- Power-Up Food: His tiger becomes fierce once Growl gives it a bit of food.
- Raised by Wolves: Growl was raised by tigers. He can communicate with them but is learning how to speak human language.
- Screw This, I'm Outta Here: Once Growl is knocked unconscious, his tiger carries him back to base.
A Peregrine Falcons recruit who seeks to find a cure for the soldiers infected by an unknown virus.
- Coat Cape: Wears her coat in this manner.
- Flipping the Bird: After defeating the Elder Centipede, she simply raised her middle finger to the creature.
- Shock and Awe: Her attacks, via her Coil Tank, emit blue lightning sparks.
An engineer of the Regular Army. She created her own personal falcon mech called Wade.
- Hyper-Competent Sidekick: In terms of combat, Victoria has a measly pistol and a knife. Wade has two rifles and can fly through enemy lines while on fire.
- Impossibly-Low Neckline: Her red shirt goes as low without exposing too much, and it isn't tied up either. Her concept art notes that her large chest had limited her clothing, and her current clothes (that she borrowed from her farm-based family) are still too small for her.
- Robot Buddy: Wade. Victoria treats it like it's an actual falcon.
- Trauma Button: While overall cheerful, she turns glum when speaking about romance. This is because she had recently been dumped by her boyfriend.
A veteran and commander of the Regular Army. She fights with the Aegis Shield.
- Shield Bash: All of her attacks consists on hitting or ramming enemies with her shield.
A police officer who patrols the streets by operating the Patrol Slug.
- Artistic License – Military: She is part of the Regular Army's MP (Military Police), except, real MPs do not wear police officer uniforms, do not use police vehicles with a red and blue sirens, nor are they assigned to patrol the streets to apprehend criminals. Her role would be more plausible if she were a civilian police from a specialized task force instead.
- Fair Cop: A police officer and quite cute.
- Immune to Mind Control: Kanae is fully immune to Psionic Brain's hypnosis waves due to focusing too hard on her patrol duties.
- Make Me Wanna Shout: The Patrol Slug has a large megaphone that emits a wide, destructive soundwave whenever the pilot speaks using their own megaphone. Kanae effectively screams at it so that the large megaphone increases in width and power.
- Transforming Vehicle: A normal patrol car turns into a bipedal mech when in combat. The two smaller wheels have weapons and are also used as shields.
Metal Device Project
A pilot of a prototype Powered Armor developed by the Regular Army's top secret weapon systems program known as the Metal Device Project.
- Almighty Janitor: In a literal sense. At the beginning of her Extra Ops, she finds herself training and cleaning instead of being the hero she wanted to be. It's to the point that soldiers depend on her to clean the mud off the corridors!
- Mundane Utility: She ends up using the armor to clean faster, to the amazement of onlookers.
- BFG: Wields a gatling gun. While she normally fire regular bullets, summoning a weapon pack allows her to upgrade to armor-piercing attacks.
- Backpack Cannon: Activating her special the first time has her summon this to her. Activating her special again allows her to fire one or two missiles from it with serious Splash Damage before detaching it.
- Clingy Costume: The armor connects to the nervous system of its pilot.
- Empowered Badass Normal: The description says the suit give its pilot the durability of heavy weaponry by using synthesized muscles created from the analysis of muscle tissue from an archdemon.
- Fiery Redhead: She's passionate and a determinator. When Marco approached her with her first mission, she can't help but jump on it.
- For Great Justice: She was chosen from numerous candidates due to her passion for justice and becoming a hero.
- Only the Chosen May Wield: It is said that few are able to use the armor. Perche is one of them.
The second volunteer of the Metal Device Project.
- Bash Brothers: With Perche. Ami's alternate victory animation and purchasable avatar suggests a more romantic interest to Perche.
- Big Eater: Downplayed. Her description has her concerned about the increase in appetite after she donned the suit.
- Energy Weapon: Uses variations of the Thunder Shot.
- Red Oni, Blue Oni: The blue to Perche's red.
- Shy Blue-Haired Girl: Possibly black haired. Perche tends to motivate her into acts of bravery.
A researcher of the Metal Device Project. Operates the Slug Defender.
- Foil: Amber is more calm and reserved while Molly is more stubborn and in-your-face.
- Genius Slob: Very dedicated to her work that she neglects personal hygiene, eating, and cleaning her room.
- The Rival: To Amber. Molly joined after noticing Amber working as a test pilot.
- Shock and Awe: Her Slug Defender attacks with electricity.
A volunteer of the Metal Device Project after losing her arm and a friend in battle.
- Arm Cannon: Her lost arm is replaced by an artificial one armed with bullets and a laser gun.
- Only Known by Their Nickname: Subverted as people call by her actual name.
Part of the same experimental power armor project as Perche and Ami.
- Born Lucky. She is the best of all the pilots. Having great compatibility with her suit far surpassing both Perche and Ami, both being envious of her massive luck.
- Energy Weapon: Her special form's attacks.
- Mighty Glacier: Cannot die as long she has her Huge Launcher in hand. Even if Ulala loses it, she can call in another one.
- Nepotism: What people accuse Ulala of getting such a position due to her parents being members of the Metal Device Project. She denies this as she has her own problems with them.
- One-Man Army. Not in game but in description. She has the power of an entire airforce division on her own making her more of a one woman airforce.
A civilian who enlisted in the Metal Device Project. Operates the Slug Rising.
- Wrench Wench: Is capable of repairing machinery, and her art has a couple of tools in her jacket.
- Signed Up for the Dental: Joined the Metal Device Project so she can take care of Molly. Molly was surprised how quickly she was able to enter a confidential part of the army.
- Team Mom: Towards Molly and Amber although all three are of similar age.
- Trademark Favorite Food: Lotus root with minced meat.
A SPARROWS recruit who also happens to be a womanizer. He is also a part of the Metal Device Project.
- The Casanova: He loves girls equally no matter the race, as long as they're cute.
- Gorgeous George: He often takes his time to look at himself in the mirror before going on a mission.
- The One Guy: Currently, the only male in the SPARROWS division.
A member of the Metal Device Project who is chosen to test pilot the Tail Slug.
- Nightmare Fetishist: Likes to tell descriptive horror stories. She also purchases Hunter Walker organs for "experiments".
- Shrinking Violet: Typically timid and docile when not speaking.
- Shock and Awe: All of her attacks are electric-based coming from the large mounted battery on the Tail Slug's back.
- The Ace: A recent academy graduate with excellent grades and a highly skilled pilot.
- Ace Pilot: The Slug Sniper has high specs but is very hard to operate, which doesn't trouble her at all.
- Expy: A redheaded female ace who pilots a mecha? She's an obvious dupe of Asuka from Neon Genesis Evangelion even before you realize the Slug Sniper has the same red-green-black color scheme as Asuka's mecha.