[[quoteright:299:https://static.tvtropes.org/pmwiki/pub/images/metroidnesboxart.png]]

->''"EMERGENCY ORDER!''\\
''DEFEAT THE METROID OF THE PLANET ZEBETH AND DESTROY THE MOTHER BRAIN THE MECHANICAL LIFE VEIN''\\
''GALAXY FEDERAL POLICE M510"''

[[TheEighties In the year 1980]] of the Gregorian Calendar, employees from the nation of UsefulNotes/{{Japan}} [[Platform/GameAndWatch advanced]] a company known as Creator/{{Nintendo}}, and [[JapanTakesOverTheWorld an age of prosperity began]]. A successful exchange of consumers and developers resulted, and thousands of video games shuttled back and forth between nations. Soon, however, MediaNotes/TheGreatVideoGameCrashOf1983 began to attack the industry, threatening galactic peace. Nintendo struck back against this aggression, but the Crash's attacks were powerful and it was impossible to withstand it in the vast reaches of the West. So Nintendo called together [[VideoGame/SuperMarioBros1 mighty video]] [[VideoGame/TheLegendOfZeldaI game franchises]] to battle the stagnant market.

In the year 1986 of the Gregorian Calendar, the company decided on a risky strategy: to send a lone space hunter game to penetrate the Crash's stronghold [[{{Metaphorgotten}} and destroy the mechanical life-form that controlled its defenses]]. The space hunter game chosen for this mission was ''Metroid''. Considered the greatest of all early shooter-adventures, ''Metroid'' successfully completed numerous missions that others had thought impossible. Despite its accomplishments, much of its hero's identity, Samus Aran, remained a mystery... unless the player beat the game in under three hours, upon which they discovered that SamusIsAGirl.

''Metroid'' successfully sold millions of units and established dozens of mechanics now standard for subsequent video games, such as secret endings, back tracking, discoverable power-ups, and SequenceBreaking. Its own legacy was continued by [[Franchise/{{Metroid}} a budding franchise]] of ''Metroid'' sequels that told the rest of the saga of Samus, and by its remake, ''VideoGame/MetroidZeroMission'', which came out in the year 2004 of the Gregorian Calendar. In ''Zero Mission'', Samus retells the story of her first adventure to a new generation, and includes a few twists in the story for her veteran fans.

''Metroid'' has also seen a number of adaptations, including a Wanpakku Comics manga that doubles as a strategy guide, and the {{Gamebook}} ''Literature/MetroidZebesShinnyuuShirei''. The gamebook notably features some AdaptationExpansion that would later be revisited in the official remake, ''Zero Mission''.

Compare to ''VideoGame/KidIcarus'' (which was built on the same game engine as ''Metroid'' and shared the same dev team) and ''VideoGame/TheLegendOfZeldaI'' (which was a major influence on the non-linear design of ''Metroid'').
----
!!This work provides examples of:

* TwentyMinutesIntoTheFuture: The 1987 ''Official Nintendo Player's Guide'' describes how the Galactic Federation was founded in the distant, far-flung year of 2000, and that Samus's mission (and, by extension, this game) takes place in 2005. It's uncertain if this was ever canon according to Japanese materials[[note]]Considering the amount of minute story details which are present and accurately represented in the guide, it's a distinct possibility[[/note]], but if it was, rest assured that [[CanonDiscontinuity it isn't any more]].
* AbilityRequiredToProceed: Samus can only do four things without items; run, jump, flip and shoot. You need the Morph Ball to even get past the first few screens, and the Missiles and Morph Ball Bombs to get anywhere. She also needs the Hi-Jump Boots and Ice Beam to access certain areas and attack the Metroids in Tourian.
* ActionGirl: [[ComicallyMissingThePoint Averted by Mother Brain, despite being female and the final boss]]; this is the only game in the series where she [[NonActionBigBad does not fight the player directly]] in her boss fight. Although [[TropeNamer there is a persistent rumor]] that SamusIsAGirl. Given Samus defeats most things by running, jumping, shooting, bombing and screw attacking, this would be a clear example of the trope played straight if true.
* AfterBossRecovery: Defeating Ridley and/or Kraid will result in Samus's missile carrying capacity being increased by 75 (granting her an extra amount of missiles of that same number). Also, both bosses have Energy Tanks hidden in or near their lairs--even if you already have six of them, it'll replenish your health. These also double as AntiFrustrationFeatures.
* AIBreaker: Ridley is normally a very hard fight, but [[spoiler:he can't hit you if you stand very close to him]].
* AirborneMook: Memus, Geegas, Wavers, Mellows, Reos, Rippers, Ripper [=IIs=], Mellas, Gamets, Gerutas, Zebbos, Holtz, Multiviolas, Rinkas... flying enemies come in a wider variety than any other type.
* AmbidextrousSprite: Present within the game itself; unique sprites for Samus facing left and right are in the ROM of the game, but are unused, though they can be seen in [[https://youtu.be/ceoxI8QdcCY commercials for the Famicom Disk System game.]]
* {{Antepiece}}: This game is hard, but the devs will sometimes precede hard parts with easier versions of the hard part to give you some safe practice. It also doubles as InstructiveLevelDesign.
** The area where you find the Morph Ball is right next to a high wall that you can jump over from one side, but traps you on the other--the only exit out is a small space that Samus can't crawl into. The only way out is to grab the power-up and then use the new power to go through it, a warm up for the next crawl space up ahead that's littered with enemies. This entire sequence also teaches the player that, while obvious in hindsight, unlike near every other platformer at the time you won't always be able to proceed by going right and will need to head in all directions in order to make progress in the game.
** As soon as you go right, you'll be attacked from above by Skrees. They move too fast for you to stop in time by shooting them from the side, teaching the player that they can shoot up to attack them. The Reo and Waver enemies also encourage the player to learn how to time Samus' flip jumps in order to dodge their patterns of movement, as the move is crucial to survival throughout the game.
** There is a difficult shaft you must climb [[http://www.2-dimensions.com/2013/05/18/the-anatomy-of-metroid-xi-shafted-again/ at the very end.]] At the start of this last level, there is [[http://www.nesmaps.com/maps/Metroid/Tourian.html a similar shaft with wider platforms.]] Even the vertical chamber in Brinstar that leads to Tourian's entrance could be considered another antepiece, given that it familiarizes players with ascending tall shafts with careful jumping and platforming.
* AntiFrustrationFeatures:
** Both Kraid and Ridley give you 75 Missiles upon killing them, which cuts down on the time spent searching for Missile Tanks, and both of their rooms have a hidden Energy Tank, which will refill your health even if you have six already.
** Any Zebetite barriers destroyed by the player will remain destroyed, even if the player dies or has to reload the game with a password. Since the act of destroying Zebetite consumes a lot of Missiles and leaves the player vulnerable to a constant onslaught of turrets and Rinkas, it is very merciful of the game developers to not force players to repeat the process every time they die to Mother Brain.
** If you're playing the game on the original hardware and have two controllers, you can press Start on Controller 1, then press Up and A on Controller 2 at the same time to end your game and go to the password screen without dying.[[note]]Pressing Up and Select while paused on the Game Boy Advance ports will yield the same result, while later releases on Nintendo's home consoles still make use of this original trick.[[/note]]
* ArmlessBiped: It is established quickly as a very successful morph in the ''Metroid'' setting with the Dessgeegas, Novas/Sovas and Sidehoppers. With the exception of the Novas, they all have the ability to walk on the ceiling, jump toward the floor and "fall" upwards.
* AwesomeButImpractical: The Wave Beam does more damage than the normal or Ice Beam, can hit the various [[DenialOfDiagonalAttack crotch monsters]], can destroy several rocks quickly and can shoot through walls. Unfortunately, you need the Ice Beam to reach certain areas and to handle the Metroids in Tourian, against which the Wave Beam does nothing. The Wave Beam is the best weapon to beat Kraid with, however.
* BigBad: Mother Brain, the mechanical life vein, is the leader of the Space Pirates and Samus's primary target, despite Metroids having the AntagonistTitle.
* {{Bizarrchitecture}}: This game has the most alien and isolating environments in the series, designed to make the player uncomfortable rather than for pacing or flow. A perfect example is the final ascent at the end; the platforms are ''incredibly'' small and awkwardly spaced, while in ''VideoGame/SuperMetroid'' and ''VideoGame/MetroidZeroMission'', the same platforms are much larger and less obstructive to the player.
* BlackAndWhiteMorality: Samus is a clear-cut protagonist, while the Space Pirates and their goal to exploit the Metroids are unquestionably evil.
* BountyHunter: Take a wild guess who. To drive the point home, the [[Platform/{{Famicom}} FDS]] version places a bag of money next to completed game files.
* BrokenBridge: The entrance to Tourian is cut off by a very high ledge with a hole that only the Morph Ball can squeeze through, with an acid pit below it. Normally, you have to kill Kraid and Ridley to activate their statues near the entrance, which will create a bridge across when you shoot them. A very skilled player [[SequenceBreaking can get across by using luring an enemy into the room, freezing it with the Ice Beam and Morph Ball Bomb jumping off of it.]]
* CallASmeerpARabbit: Polyps and Dragons have a superficial resemblance to what those words are meant to describe at best, although at least Dragons do resemble [[SeahorsesAreDragons seahorses]].
* CheckpointStarvation: Since this game precedes the introduction of Save Stations in the series, there are five checkpoints in the entire game, and all of them are at the start of each area you enter.
* ClassicCheatCode
** By ''accident''; the famous '''JUSTIN BAILEY''' code is just a side-effect of the password calculation system and is but one of many codes that bestow Samus with a leotard. The far less famous '''NARPAS SWORD''' ('''[[FunWithAcronyms N]]'''[[FunWithAcronyms ot]] '''[[FunWithAcronyms A]]''' '''[[FunWithAcronyms R]]'''[[FunWithAcronyms eal]] or North American Release Password) actually ''is'' a special, unique password, however.
** '''[[https://www.youtube.com/watch?v=x3UyVylP7AI ENGAGE RIDLEY MOTHER FUCKER]]'''. Sadly, that code has now become a system-killer in the 3DS port. Using it on a NES emulator will also crash the game on the spot.
* CollapsingLair: Once you destroy the Mother Brain, a bomb timer starts counting down. You have to reach the top of a long vertical shaft filled with ''very'' small ledges in order to escape and finish the game. If the timer hits zero, the place blows itself to kingdom come and takes Samus with it.
* CollisionDamage: Every enemy, except for the dragons which try to shoot Samus, Skree which try to [[ActionBomb explode]] near Samus and the Metroids who try to latch onto Samus, rely on this. The bosses Ridley, Kraid, Fake Kraid and Mother Brain have projectile attacks but can still cause collision damage.
* ContinuingIsPainful: Every time you get killed or use a password to continue where you left off, you spawn with '''only 30 Energy'''. A [[http://www.romhacking.net/hacks/1186/ patch]] for the ROM not only adds the saving system, but also saves your health (no grinding to regain your health after loading!) and offers a (although minimalist) map screen!
* ConvectionSchmonvection: Unlike later games, the Varia Suit is not needed at all in Norfair, as all it does is cut the damage from enemy attacks in half. Exaggerated in that she can even go into the area wearing nothing but a leotard and knee-high boots, and she still takes no heat damage unless she directly touches lava.
* CopyAndPasteEnvironments: One of the reasons that the original is [[NintendoHard hard as hell]], especially for people who played the sequels; this was, however, crucial in making a fairly large world without running out of cart space. The upshot is that many of the secret area entrances are copy-and-pasted as well, so finding one can make it easier to find others in the same area.
* CoresAndTurretsBoss: Mother Brain does not attack Samus directly - she instead relies on her turrets, lava pools and Rinkas to attack her while she sits still.
* CriticalAnnoyance: Whenever Samus Aran's energy gets low enough, you're treated to the [[SarcasmMode lovely]] sound of "beep beep beep beep beep beep beep beep beep beep beep beep..."
* CriticalExistenceFailure: Getting to zero health results in Samus's ''entire body'' exploding instantly. Same goes for Ridley and Kraid, who show no sign of injury before suddenly exploding the instant they are defeated; at least Mother Brain starts pulsating more frequently as she takes more and more damage.
* DamnYouMuscleMemory: Samus controls differently in this game compared to later titles, making it all too easy for franchise veterans to make simple yet costly mistakes while playing this entry. For example, she cannot shoot down or [[DenialOfDiagonalAttack diagonally]] at all; pressing Down and B causes her to go into Morph Ball mode and drop a Bomb, rather than crouch and fire; pressing up in midair will prevent Samus from aiming left or right until she touches the floor; and her Screw Attack is canceled out by letting go of the jump button or by touching the ceiling, leaving her vulnerable in narrow spaces.
* DenialOfDiagonalAttack: The game only lets you shoot horizontally and straight up, and you can't duck. The Wave Beam helped deal with this, but you inevitably needed to replace it with the Ice Beam to deal with the Metroids. The Screw Attack was awesome enough to possibly qualify for a partial aversion for flying enemies, but the only other way to deal with crotch monsters was with Bombs.
* DependingOnTheArtist: There are two artstyles used for ''Metroid'' artwork: a [[http://www.metroiddatabase.com/wp-content/uploads/Metroid/Artwork/m1art_brinstar.jpg gritty]] [[http://www.metroiddatabase.com/wp-content/uploads/Metroid/Artwork/m1art_norfair.jpg realistic]] style used in the instruction booklet (in both the Japanese and Western versions) and a [[http://www.metroiddatabase.com/wp-content/uploads/Metroid/Artwork/jpguide1_enemies_Brinstar.png cute]] [[http://www.metroiddatabase.com/wp-content/uploads/Metroid/Artwork/jpguide1_enemies_Norfair.png chibi]] style used in the Japan-only strategy guide. Most characters and creatures, including Samus and Kraid, have consistent designs between the two artstyles, but Ridley is a notable exception. In the instruction booklet, Ridley's head has a very alien design with two large bug eyes, three ExtraEyes along his snout, and a tube-shaped mouth. In the guide, Ridley's head appears more similar to that of a traditional western dragon, removing the extra eyes and tube-mouth in favor of long toothy reptilian jaws. What makes this notable is that the former design is EarlyInstallmentWeirdness while the latter design much more closely resembles his iconic modern design later introduced in ''VideoGame/SuperMetroid''.
* DifficultyByRegion: {{Zigzagged|trope}}, as enemies in the Famicom Disk System version tend to have more complex patterns than their NES counterparts, making combat more difficult. All the same, the FDS still lets people save their game. The FDS has less lag too, meaning the player will take less cheap hits. The NES version also requires you to beat the game in one hour to get the best ending, whereas the FDS version gives you two.
* EarlyGameHell: You start off with only a short range blaster and what amounts to a few hit points worth of health. Once you get a few energy tanks, the weapon upgrades and the Varia Suit, the game gets significantly less hard.
* EarlyInstallmentCharacterDesignDifference:
** Samus is a brunette with EightiesHair, not a pony-tailed blonde. She also has a leotard under her armor, instead of the Zero Suit seen in ''Metroid: Zero Mission'' onwards. Samus's Power Suit used the traditional orange, yellow, and red color scheme while the Varia Suit swapped out the orange with pink. Future games would make the Power Suit more yellow while the Varia Suit gained the Power Suit's old colors.
** Kraid is hairy and [[http://images2.wikia.nocookie.net/__cb20100501204216/metroid/images/9/94/Samus_artwork_11.png the same height as Samus]]. Mother Brain has a defined face with two eyes instead of a single large eye. Ridley stands out the most, as while he still looks like a dragon in his sprites, the manual instead depicts him as [[https://static.wikia.nocookie.net/metroid/images/4/4e/NES_Metroid_HQ_Ridley_artwork.png a fat alien with a multi-eyed, leech-like head]] who, like Kraid, is also much smaller than he would later be depicted.
** The manual art depicts Metroids with tentacles, as opposed to the talons they bear in their sprites and future games.
* EarlyInstallmentWeirdness: Several gameplay mechanics feel absolutely weird, especially if one plays the later ''Metroid'' games first before playing this one.
** The game has no map.
** Samus cannot duck, nor can she shoot downwards while jumping. This makes it impossible for her to shoot any enemy who's on the same plane if they are shorter than she is, unless she has the Wave Beam.
** When missiles are equipped, rather than her arm cannon opening up like in all subsequent games, Samus simply changes color.
** [[ContinuingIsPainful Samus always starts at 30 energy points]] after you load your saved game/use a password, regardless of your Energy Tank collection. There are no health or ammo recharging stations, either.
** Only the default beam, Ice Beam, and Wave Beam are in the game. The default beam doesn't even shoot across the entire screen and requires the "Long Beam" power-up to do so (which was never used again except in the [[VideoGame/MetroidZeroMission remake]]). Also, the beams don't "stack" like in later games; for example, in [[VideoGame/SuperMetroid Super Metroid]] the effects of the Charge Beam, Ice Beam, Spazer, and Wave Beam are all cumulative, whereas in the original game Samus can only use one beam at a time.
** The back of the box says that, "left alone the Metroid[s] are harmless," when later games make it fully clear that Metroids are ''always'' dangerous and the Pirates are idiots for trying to control them. The very next game even has Metroids be deemed such a large threat that the Galactic Federation orders their extermination.
** Blue doors close after a set period of time if you do not enter after shooting them open. Red doors, meanwhile, never close after being shot open; in later games they change into a normal blue door when you revisit that area.
** This is the only game in the series where Samus's gender isn't clear right away, with even the manual referring to her using male pronouns, in both the Japanese and English versions. Later installments consistently use female pronouns and show her without her armor in various cutscenes and death animations, making the secrecy and "twist" in the original seem out of place in retrospect.
** Since there are no door locks that require enemies to be killed to open them, the Metroids do not actually have to be defeated to proceed through Tourian. They can be frozen and ignored.
** Tourian has special orange locked doors that require 10 Missiles to open. These are never seen again anywhere else in the entire franchise.
** There are no generic Space Pirate enemies whatsoever -- Kraid, Ridley, and Mother Brain are the only members seen. They do imply at this point that the various lifeforms scattered throughout are supposed to be members of the gang, but later games would give us proper humanoid enemies filling that role.
** The manual claims Ridley is a native Zebesian who is controlled by Mother Brain. Future games never state that Ridley ever hailed from Zebes, and while he continues to loyally serve Mother Brain in ''Super Metroid'' and ''Zero Mission'', he does so willingly rather than being forcibly controlled. He's also depicted as just another monster for Samus to fight, rather than her intensely personal ArchEnemy.
** By beating the game fast enough, the game can be replayed with a suitless Samus (though this is merely a graphics swap). While ''Zero Mission'' and ''Other M'' would feature a temporary segment where an unarmored Samus can be controlled, no other games to date have featured a full "suitless mode" as this game does.
** Respawning breakable blocks can actually hurt you if you stay in place. The sequel still did the same thing before eventually being fixed in VideoGame/SuperMetroid.
** There are no save stations in the game and the ability to save was only present in the Japanese version while a password was used everywhere else. The next game would introduce save stations. Likewise, ammo refill stations weren't a thing until the sequel onward.
** Samus's gunship wasn't present in the original game, though the ''Zero Mission'' remake would show it off.
** The Ice Beam is required in order to progress past the Metroids. If the player doesn't have it, they'll have to make a long trek to a Chozo statue to get it. The sequel did the same thing as well while later games would give the player everything they needed to beat the game without missing anything.
** The countdown time is placed where your missile count is instead of having its own spot on the hud. The countdown message is also just placed on the spot where Mother Brain was when she is defeated.
* EarnYourBadEnding: Getting the two No Frills endings requires you to beat the game in over five hours. In a normal playthrough, Samus raises her fist in victory, but the armor stays put. Doing this with Armorless Samus will have her back toward you and her arm thrown over her face in shame.
* ExcusePlot: Sure, there's some backstory in the game, and the scope of it is greatly expanded upon in the sequels, but here, you're just a bounty hunter on a mission to blow up some space aliens.
* FakeDifficulty: A big reason why the game is so hard is because it uses a lot of cheap difficulty tricks; there's no map, so unless you use a guide, a lot of the items have to be found through TrialAndErrorGameplay--the CopyAndPasteEnvironments do not help at all. And no matter how many energy tanks you collect, Samus will always start with 30 hit points, forcing a player to [[FakeLongevity waste a lot of time farming for health]] (especially if you have all of the tanks), and all that health can easily be whittled away by the merciless barrage of enemies due to Samus' weak stamina (although the Varia Suit helps mitigate this) and lack of MercyInvincibility--and if you die, [[ContinuingIsPainful you go right back to having 30 HP again]]. To make matters worse, there are more than a few spots where it's extremely hard, if not impossible, to dodge certain enemy attacks. On top of that, Samus' jump is very floaty and she can be easily knocked back on contact with an enemy. Norfair also has some deep pits that are extremely hard to jump out of, even with the Hi Jump Boots. Oh, and there's no save stations, so if you die in one of the five areas, [[CheckpointStarvation you have to start right back at the beginning of each of them]] (the only mitigation being that you get to keep whatever items you collected already).
* {{Foreshadowing}}: The first Metroid, while theorized to be a dangerous energy draining entity that could multiply if exposed to beta rays for 24 hours, is discovered in [[HumanPopsicle suspended animation]]...frozen. Which weapon was needed to defeat them again?
* FrozenFoePlatform: The Ice Beam's traversal use in shooting enemies. Many areas can only be accessed by freezing enemies, such as the first game's Rippers, and making use of them as platforms before they thaw.
* GameplayAndStorySegregation: Despite the Metroids being built up as the ultimate threat of the game to defeat, destroying them or even fighting them is completely optional (avoiding them is possible, but ''extremely'' difficult). Destroying them has no bearing on the gameplay either, as they simply respawn. You can freeze them and move on if you want to conserve energy and ammo, or fight them and stand a good chance of getting big energy/missile refills.
* GlitchEntity: The invincible frozen Zebetites and Mother Brains in the secret worlds found using the door glitch.
* TheGoomba: Zoomers, the most common enemy and the first you encounter. Like [[VideoGame/SuperMarioBros1 actual Goombas]], they move around nimbly, but that's it--they don't even directly attack you. They only take a couple hits to kill, but you can't hit them while they're on your ground level due to the game's inability to crouch or aim at an angle, so you have to jump over them, use bombs to dispatch them, or have the wave gun.
* GraphicsInducedSuperDeformed: There are many glaring examples, most obviously being the Metroids themselves! Official art depicted them with ''tentacles'' but the sprites made it look more like them latching on with teeth/mandibles. Official art of later games actually ''did'' give Metroids mandibles rather than tentacles, both in official art as well as their sprites/models, but their ''VideoGame/KidIcarus'' counterparts Komayto, [[DivergentCharacterEvolution continued to be depicted with tentacles]], while ''Videogame/MetroidPrime'' and [[VideoGame/MetroidPrime3Corruption its second sequel]] added three tentacled Metroid offshoots.
* GuideDangIt: Pretty much everything. Between the constant repetition of room layouts, the lack of a map, and the many, many secret passages and hidden items you'll need to find (not a single one of which is hinted at anywhere), a guide is practically mandatory for your first playthrough.
* HardLevelsEasyBosses: The levels are loaded with hazards and hostile wildlife that will make short work of you if you let your guard down. The boss fights aren't a total cakewalk, but they're much less challenging in contrast, especially since two of the bosses (Ridley and Mother Brain) just stay stationary while attacking you with projectiles, while you spam missiles at them in turn. Kraid is tougher, but still much easier than his ''brutal'' lair.
* HeartContainer: Energy Tanks. There are two more of them than the maximum number you can have, and they fully restore energy upon collection, so save one for your final run... [[OneHundredPercentCompletion or don't]].
* HornAttack: Geegas apparently have "poison" in their horns. Also, Zebs and Gamets.
* HumanoidAliens: The only evidence of aliens with human-like body structure are the Chozo statues, which resemble BirdPeople - though some official art suggests they had exoskeletons rather than skin and feathers, and assuming the bird-like alien in the manual is supposed to be a Chozo. There are actually several humanoid aliens in the manual but no evidence for them is seen in any game until ''VideoGame/SuperMetroid''.
* HyperDestructiveBouncingBall: Multiviolas, which get faster the deeper into the planet you go.
* InASingleBound: The High Jump Boots, which are not required, but makes the various secret passages that end up going nowhere much more bearable.
* InconsistentSpelling: The game's intro spells the planet the game takes place on as "Zebeth", as opposed to the manual and future games, which use "Zebes". A few enemies are also spelled differently in the manual compared to how they are spelled in later games (Reos, for example, are spelled as "Rio").
* LateArrivalSpoiler: Later games make it obvious Samus is a woman from the start, and address her with female pronouns, making TheReveal obvious to modern players.
* LethalLavaLand: Norfair, Ridley's Hideout and Tourian. Brinstar and Kraid's Hideout seem to use super-corrosive acid instead. Hacking the game reveals that ''every'' horizontal room has the lava/acid effect hard-coded into it to save on game memory; the tiles are either changed or covered up with solid ground so it won't harm the player.
* LifeEnergy: According to the instruction manual, the cyborg known as Samus has a space suit that can absorb the power of those "he" defeats to replenish his health and restore "his" ammo, which is why the space pirates ([[OddlySmallOrganization all three of them]]) fear "him." Metroids can drain life energy directly from hosts, quickly killing them.
* LoadsAndLoadsOfLoading: The Famicom Disk System version has nearly a minute of loading every time Samus enters a different area.
* LoadBearingBoss: After defeating Mother Brain, a warning telling you that Tourian will soon self-destruct will appear along with a [[ExactTimeToFailure timer]] showing how long until this happens. Samus must climb a (very repetitive) tower just past the door to the left before the time runs out, [[TakingYouWithMe killing her.]]
* MadeOfIron: Despite initial impressions, the weaker Rippers ''can'' be killed by your normal beam weapon--100 beam shots, to be precise. You're better off just freezing them with the Ice Beam or blowing them up with a single missile. Their hardier counterparts are immune to everything, even your ''Screw Attack!''
* MercyInvincibility: Part of why the game is so hard is that Samus' mercy invinciblity lasts less than ''1 second''.
* MinusWorld: The game's [[https://www.youtube.com/watch?v=IMEnsIhtpsY glitchy secret worlds]] can be accessed by getting yourself stuck in doors, are many times larger than the 'real' map, and inspired vast numbers of conspiracy theories before it was proven they were caused by the game reading its own code as level data. They are also abused for {{Speed Run}}s.
* MookMaker: Air tubes, which make progressively faster and more damaging mooks the deeper into Zebes you go.
* MultipleEndings: There are five, all earned based on how quickly you beat the game:
** Beat the game in over five hours, and Samus raises her fist in victory, but the armor stays put.
** Beating the game in over five hours with Armorless Samus will have her back toward you and her arm thrown over her face in shame.
** Beating it between 3 to 5 hours makes Samus' helmet disappear.
** Beating it in less than three hours makes Samus' armor disappear, revealing a purple leotard. Pressing Start at the end of the credits allows you to [[NewGamePlus start a new game as Armorless Samus.]]
** Beat the game in less than an hour (two in the FDS version), and Samus will be shown wearing a bikini.
* MutuallyExclusivePowerups: One cannot hold the Ice Beam and the Wave Beam at the same time, requiring those with one wanting the other to go back to where they initially found it (they respawn once Samus picks up the opposite beam). Inputting the NARPAS SWORD code (which grants the player every powerup save Energy/Missile Tanks) or any other custom password that flags Samus as having both gives a beam that behaves like the Ice Beam, but with a blue colored Wave Beam sprite.
* NewGamePlus:
** After beating the game you get to keep all of Samus's power-ups for future times playing through except for her Energy and Missile Tanks, which you have to find again. Still, it can allow you to finish the game much faster...
** ... and if you beat the game in under three hours (or just get the password from someone else), you can play through the game without the Power Suit, with all the controls and power ups still working the same for an unarmored Samus. Just a one time thing for this game though - this reward never crops up again, and when you do play as an unarmored Samus in ''VideoGame/MetroidZeroMission'', she's much weaker without it (here, the unarmored look is cosmetic more than anything).
* NewWorldTease:
** The entrance to Kraid's Lair is the second room you enter in the game, but you can't access it until you get the Morph Ball Bombs. Likewise, only a small section of Norfair is accessible without bombs.
** The room leading to Tourian is accessible early on, but Kraid and Ridley have to be killed to activate the bridge allowing access to its entrance.
* NintendoHard: This game is likely the hardest in the series - the lack of a map combined with CutAndPasteEnvironments makes it easy to get lost, and the enemies/bosses can hit hard without the proper power ups. There's a save feature in the FDS version, but you can't save whenever you want - only when you die. Plus, you respawn with only 30 units of health, so you have to grind to regain your remaining health (or hunt down an Energy Tank). Trying to beat the game with only the three mandatory power-ups (Morph Ball, Bombs and Missiles) makes the game even harder.
* NonActionBigBad: Mother Brain lets her minions attack and automated defenses hinder you rather than do anything herself. She's been more active in every reappearance.
* NonIndicativeName: Rippers, the common, slowly floating enemy you usually find in horizontal tunnels. While they're very hard to kill with your normal beam, they don't even try to attack you--in fact, it's better just to freeze them with your Ice Beam so they can be used as platforms. Even its Norfair counterparts are barely any more threatening, aside from moving faster.
* NoSidepathsNoExplorationNoFreedom: In stark contrast to the rest of the game, [[TheVeryDefinitelyFinalDungeon Tourian]] is a very linear, straightforward level with no power-ups, where your goal is to fight your way past the Metroids, reach Mother Brain and then destroy her.
* OddlySmallOrganization: The Space Pirates are hardly the fearsome force the manual make them out to be. The local fauna and general geography are your most constant dangers in their so-called base. They managed to steal quite a lot of Metroids all the same. The manual claims Mother Brain gave life to the Multiviolas, but they still aren't referred to as Space Pirates, only "eerie followers" of them. The strategy manga for the game added a bit of plot, explaining Samus defeated most of the space pirates in space, but then fell off her ship (the vessel seems to be a bit of a klutz when Samus isn't piloting it or giving it orders), requiring her to find new power ups when she landed on the planet without it.
* OffscreenStartBonus: The Morph Ball is placed just to the left of the starting point. You can't progress more than a few screens to the right without it, so it serves to demonstrate to new players that you ''can'' go left -- which was important at the time, as most platformers of that era held firm to the principle of WhenAllElseFailsGoRight.
* OneBulletAtATime: Samus can have three beam shots on screen and three bombs, but only one missile, despite having a "rapid fire missile attack" in the strategy guide manga.
* OneHitKO: Hitting any regular enemy with a missile or the Screw Attack will always inflict this on them.
* OpeningTheSandbox: You start off with just a meager blaster, and getting the Morph Ball allows you to get past the first few rooms. Getting the missiles and the Morph Ball Bombs basically let you explore anywhere you want--the rest of the items are needed so you can have a fighting chance of survival while you explore, although the Hi-Jump Boots and Ice Beam are needed to access certain areas.
* PaletteSwap:
** Activating missiles turns Samus's arm cannon blue when in her armor. The Varia Suit upgrade turns her armor white (pink/purple when missiles are activated). Unarmored, the Varia Suit turns Samus's hair and gun from brown to green (and adds some green pixels to her boots).
** A few enemies are also palette swapped, usually appearing together in the same area (typically, one variant takes twice as many shots to kill as the other) while other enemies with the same function get different sprites in other areas. Particularly, red/brown Metroids are slow but more likely to come after Samus while green Metroids are fast but likely to lie in wait ([[ArtificialStupidity or get caught on bits of scenery]]).
** Fake Kraid is physically distinct from Kraid by being brown with blue hair and not yellow with green hair.
* PivotalBoss: Ridley's movement is limited to jumping in place and turning around if you get behind him.
* {{Portmanteau}}: The name ''Metroid'' is a mashup of the words ''Metro'' and ''Android''.
* PowerDyesYourHair: Samus has brown hair when in her "Justin Bailey" leotard, but getting the Varia Suit powerup turns her hair green to show it's working.
* PowerupLetdown: The Ice Beam kinda sucks in this game. Freezing an enemy deals no damage, only ''un''freezing them does that. This means twice as many shots to kill something. Of course, you won't think it's a letdown once you go to Tourian...
* PrecisionFStrike: The random password generation somehow gave two notable passwords with the word "fuck" in them. ENGAGE RIDLEY MOTHER FUCKER is the more popular of the two, although it's known for bricking 3DS systems and isn't playable anywhere else. MOTHER BRAIN? FUCKIN TOASST, [[MeaningfulName by some bizarre twist of fate]], spawns Samus in Tourian suitless with every upgrade but the Long Beam and Morph Ball with Mother Brain dead.
* {{Railroading}}: The game is very non linear and gives you a lot of freedom, but it uses this to give the player some sense of direction while you start OpeningTheSandbox. You can't even get past the first few rooms without finding the Morph Ball. To access Kraid's Lair, most of Upper Norfair, Lower Norfair and many other rooms, you need the Morph Ball bombs. And to access many rooms, including the boss rooms and rooms with items, you need to have at minimum five missiles to blow open their locked doors. And to access Tourian, both Kraid and Ridley need to be killed.
* RedHerring: There exists a look alike of Kraid that dies in one hit, though to find it, you have to go pretty far off course so most players do not see it.
* RegionalBonus: The NES version has a NewGamePlus and a [[DebugRoom Debug cheat]], which weren't in the FDS version of the game. Armorless Samus is not playable in the Japanese version at all.
* RockMonster: The manual says Polyps are living, poisonous lava, though to the player, they may as well be lifeless geyser hazards.
* SamusIsAGirl: Beat the game fast enough to get any but the worst ending, and Samus will take off some or all of her armor, revealing a feminine face and [[LongHairIsFeminine hair down to her back]]. To sell the twist, the manuals outright lied and repeatedly [[GenderConcealingWriting referred to her with male pronouns]] -- even in Japanese where they could've easily gone with gender-neutral pronouns instead.
* SequenceBreaking: The game started a series wide tradition of doing this thanks to some tricks you can pull off. Many of these tricks are frequently used in speedruns.
** The Morph Ball, Bombs and Missiles are the only things absolutely required to beat the game (making seven power ups optional), though you will probably need the Ice Beam too if running an absolute minimum run.
** A "Bomb Boost Jump" can be performed by laying a bomb and unmorphing before it detonates. Samus will be sent into the air by the bomb, and she can jump higher than normal.
** If Samus rolls off a ledge in Morph Ball form and unmorphs, she will be in her standing sprite, and she is able to jump.
** The Varia Suit can be collected without the Ice Beam by Door Jumping up to the Varia Suit's room in the shaft that is two rooms from the Varia's location.
** The Varia can also be collected without the High Jump Boots but with the Ice Beam. Samus must abuse a Waver by freezing it over and over to get to the Varia. The Waver may not always line up correctly though.
** Ridley's Lair or the area leading to the High Jump Boots can be reached without the Bombs by using the [[http://metroid.wikia.com/wiki/Door_Jump "Door Jump" glitch]] in the "green bubble" area of Norfair.
** The Ice Beam can be collected without the Bombs by using the Door Jump.
** Kraid and Ridley do not have to be defeated to get into Tourian. If Samus lures a Reo from Corridor Number Two into the room with the Stone Statues and freezes it above the acid, she can perform a difficult Bomb Jump to reach the other ledge.
* SequelHook: The game's ending warns that while Samus succeeded in her mission and restored peace, it may be invaded by the other Metroid(s). This is followed up in ''VideoGame/MetroidIIReturnOfSamus''.[[note]]Though in a superb bit of {{Irony}}, it winds up being ''Samus'' who "invades" the Metroid homeworld.[[/note]]
* ShoutOut: Ridley, whose name is derived from Creator/RidleyScott, the director of ''Film/{{Alien}}'', a huge influence to ''Metroid''. Mother Brain is likely also a reference to MOTHR, the obstructive AI of the ''Nostromo''.
* SoNearYetSoFar: You can reach the entrance to Tourian almost immediately after getting the Morph Ball and Missiles, but you can't actually get past the statues to the elevator room until you kill Kraid and Ridley.
* SpoiledByTheManual: The instruction manual details almost everything in the game. Emphasis on "almost", for when they get to the EscapeSequence, all they said was, "If you manage to destroy the last enemy, Mother Brain, wait for a message to flash across the screen a second later. Something big is in store for you! We can't disclose it here, but we can tell you that the game is not over yet!"
* StationaryBoss: Mother Brain, who does not directly attack at all but waits at the end of a locked down death course.
* UndergroundLevel: The whole game is one big one. The only time Samus appears above ground is in the ending.
* UnwinnableByDesign: Downplayed. Mother Brain and the barriers that protect her are ''only'' vulnerable to missiles, so if you run out, you have no way to win. You must kill yourself and respawn, most likely farming Metroids in order to get more missiles [[ContinuingIsPainful (and health)]].
* VagueHitPoints: Enemies usually die in a few hits, so HitPoints don't have to be indicated.
* TheVeryDefinitelyFinalDungeon: Tourian. The entrance is blocked by a bridge that requires Samus to be in ball form to cross, but has a huge hole in the ground. You must [[SequenceBreaking (normally)]] defeat both Kraid and Ridley, then shoot the statues of them to create a bridge to get there. Tourian is a short area, but it has very deadly enemies, the whole area is grey in color, and the music is the same as what you hear during the fights against Kraid and Ridley.
* ViolationOfCommonSense: There exist quite a few expansions and power ups hidden under fake pools of acid or lava, most of which you have to go out of your way to fall in.
* WallCrawl: Zoomers, Zeelas, Violas and Sovas do this. Until you get bombs you have to wait for them to crawl on a wall if you want to get rid of them.
* WickedWasps: Zebbos are basically giant flying vespids.
* WhamShot: It's the 1980s and Samus Aran is the manliest man who ever put on a space suit. Getting him through this masochistic adventure was not enough for many players then, they wanted to do it quickly enough to see him take off his helmet... or rather, ''[[SamusIsAGirl her]]'' helmet. Do it even quicker and she takes off the suit entirely, wearing underneath it a leotard that reinforces that she is in fact, a woman and not just a long-haired man.
* WhenAllElseFailsGoRight: ''Extremely'' averted. The Morph Ball is placed to the left of the start point, just to teach the player that going left is a thing, and even the tiny detail of ''Samus's starting pose'' averts this (she faces the screen, to avoid suggesting that right is "forward").
* YouHaveResearchedBreathing: Samus needs a power up just to be able to crawl through small chasms and another to shoot her beam more than a few feet in front of her.
----