is a series of nonlinear science fiction action games published by Nintendo, featuring side-scrolling, metroidvania, and first-person shooter elements. The player character and protagonist of the series is Samus Aran, a space-faring bounty hunter who battles Space Pirates and a species called the Metroid.

Major characters Samus Aran

is a bounty hunter and the protagonist of the series. Prior to the events of the series, her homeworld was attacked by the Space Pirates, and her parents were murdered by their leader Ridley. This led to her being taken in by the Chozo aliens, who saved her life and raised her to become a warrior. She wears a futuristic suit equipped with armor, blaster cannons and other weapons such as missiles. The additional protection provided by the suit allows Samus to survive on other planets. Samus also appears in the Super Smash Bros. series as a playable character.

Ridley

is a high-ranking Space Pirate and major recurring antagonist who serves as Samus's archenemy. He has been defeated by Samus multiple times and was the final boss in Metroid: Samus Returns. Despite these defeats, he is always revived by the Space Pirates (or accidentally by the Galactic Federation in Metroid: Other M) using cloning or robotics. Other than Samus and the titular Metroids, Ridley is the only character to appear somewhat consistently throughout the series. He is directly responsible for the invasion of Samus' home planet and the death of her parents and is the franchise's most frequently recurring villain.

Outside of the Metroid series, Ridley (in cyborg form) is a boss in the campaign of Super Smash Bros. Brawl and Super Smash Bros. 4, and a playable character in Super Smash Bros. Ultimate.

Mother Brain

is a brain-like supercomputer and the main antagonist of Metroid, its remake Metroid: Zero Mission, and Super Metroid. The Chozo created it as a councilor, and as a means to "accelerate their plan to link the galaxy into one unified society". Mother Brain is depicted as a large brain with cybernetic spikes and a single eye, usually contained in a glass tube which Samus must break in order to injure it. In Super Metroid, Mother Brain also rises from the floor and reveals a grotesque body after her tank is destroyed.

In the Metroid manga, during the Space Pirate invasion of Zebes, it sees the Space Pirates as a "perfect force capable of restoring true order to the universe", and successfully established itself as one of their leaders. At the same time, Mother Brain attempts to persuade Samus to be an ally in order to "build a new age for the universe" by claiming that because it built the power suit that Samus wears, she is indebted to Mother Brain.

Samus seemingly destroys Mother Brain in the original Metroid, but again confronts it in Super Metroid. It was revealed in Metroid Prime 3 that the Galactic Federation had constructed biomechanical supercomputers called Auroras, and that there were plans for a "Future Aurora Complex", which appears to be the Mother Brain depicted in Super Metroid. The main antagonist of Metroid: Other M, MB, is an android housing an AI cloned from Mother Brain's genetic material from Samus' suit.

Adam Malkovich

Samus' former commanding officer in the Galactic Federation army, he only appears in person in Metroid: Other M, in which he plays a major role. Initially skeptical of accepting her help with his team's mission, he eventually serves as Samus's commander for the duration of the game. Samus and Adam are shown to have had a very close relationship, with her seeing him as a surrogate father. Adam is also notable for his commitment to the greater good even at personal cost: in the past he had allowed his brother to pass away in order to avoid risking the deaths of Samus and his team, and upon entering the Sector Zero area of the game, he activates the laboratory's self-destruct protocol, sacrificing himself to save Samus again. In Metroid Fusion, it is revealed that the Navigation Computer of Samus's new ship is Adam Malkovich's consciousness in computer form. This computer consciousness returns in Metroid Dread, albeit impersonated for most of the game by Raven Beak.

Raven Beak

Raven Beak is the leader of the Mawkin, a Chozo warrior tribe, and the main antagonist of Metroid Dread. He and the Mawkin aided the Thoha, a fellow tribe of the Chozo, in containing the Metroids on SR388, and also gave some of his DNA to Samus. However, after learning that the Thoha intended to destroy the planet to get rid of the Metroids, he murdered them all except one: a scientist named Quiet Robe, whose control over the Metroids was necessary to use the creatures as a tool to take over the galaxy. He is shown to be both cunning and powerful, luring Samus and the Galactic Federation to the planet ZDR with footage of X parasites before ambushing and nearly killing Samus. He then pretends to be Adam, putting her through numerous hardships during her mission to get her to awaken her Metroid powers before asking her to join him. He is ultimately killed by Samus in a final confrontation.

Metroid Prime / Dark Samus Metroid Prime is the titular main antagonist and final boss of Metroid Prime. Its later form, Dark Samus, is a major antagonist in Metroid Prime 2: Echoes and the main antagonist of Metroid Prime 3: Corruption.

As Metroid Prime, it is a strange, black-carapaced, red-eyed creature with a humanoid face within its shell and the ability to control and horribly mutate anything it attaches to. Metroid Prime was formed when a Phazon meteor known as a Leviathan impacted on the planet Tallon IV, released its living core, and fused with a Metroid. It caused severe damage to the Chozo colony before the Artifact Temple was built to contain Metroid Prime inside the impact crater of the Leviathan, where it remained until the events of Prime (although to what degree differs between versionsMetroid Prime, NTSC version. Space Pirate Data "Metroid Prime": Test subject Z-d, hereafter referred to as Metroid Prime, was recently discovered in a cavern by mining crews.Metroid Prime, NTSC version. Space Pirate Data "Prime Breach": Subject Metroid Prime's breach has been contained. Reports indicate that it sensed a large batch of raw Phazon in the lab from within its stasis tank and broke through the glass, using previously unsuspected strength. Besides consuming all of the Phazon, Metroid Prime assimilated several weapons and defense systems from fallen security units.Metroid Prime, PAL version. Space Pirate Data "Impact Crater": Investigations into a possible ingress point for the impact crater continue to meet with failure. The shield of strange energy that protects it is impermeable, and all attempts to tunnel past it have proved fruitless. Our continued futility in this matter is made all the more significant in light of recent life form readings we've discovered emanating from deep within the crater.).

After its defeat, the creature takes Samus' Phazon Suit to reconstruct itself into a body similar to hers, resulting in the being referred to as "Dark Samus." In Metroid Prime 2: Echoes, Dark Samus arrives on Aether while chasing the planet's Phazon. Shortly after, Samus arrives and encounters Dark Samus many times, eventually defeating her as Dark Aether was destroyed, but a post-credits scene shows Dark Samus reforming herself in deep space.

Metroid Prime 3: Corruption Dark Samus has brainwashed the Space Pirates to be their leader, and begins her mission to spread Phazon across the universe. In an attack to the Galactic Federation vessel G.F.S. Valhalla, Dark Samus steals a supercomputer, the Aurora Unit 313, which is used to implant a computer virus into the Galactic Federation's network of Aurora Units, crippling it. Shortly after, Dark Samus leads an attack on Norion, corrupting Samus and other bounty hunters with Phazon. After Samus destroys the Leviathans of four planets, she goes to Phaaze, where she finally defeats Dark Samus, who then merges itself with the Aurora Unit 313 in a last-ditch effort to defeat Samus. After the Aurora Unit is destroyed, Phaaze explodes, and all Phazon in the galaxy is rendered inert.

Dark Samus appears in Super Smash Bros. for Nintendo 3DS and Wii U as an Assist Trophy and an alternate costume for Samus. She became a playable character in Super Smash Bros. Ultimate with a similar set of moves to Samus.

IGN listed Dark Samus as the 88th best video game villain, describing her as being a "creepily evil doppelganger" that never truly dies. TheGamer listed her as the 6th best Metroid character, calling her "one of the most evil and horrifying entities in the series." GamesRadar+ ranked her as being the 4th best fictional evil clone, praising the fact that "[while] evil clones in other games tend to be one-off gimmicks, [she] endured long enough to be the central villain", and stating that unlike "other dark clones [who] just want to bump off their originals, Dark Samus wanted to conquer, and she came awfully damn close – and may come back to do so again".

Sylux

Sylux is a bounty hunter and former Federation trooper, first appearing as a recurring antagonist in Metroid Prime Hunters and later as the main antagonist of Metroid Prime 4: Beyond. He is considered to be Samus' rival, harboring a great hatred towards her and the Galactic Federation as a whole. His main weapon is the Shock Coil, an electric-based prototype weapon stolen from the Galactic Federation, which drains energy. He can also transform into an alternate form called the Lockjaw, which acts similarly to Samus' Morph Ball, and has a ship named the Delano 7.

In Metroid Prime Hunters, Sylux and five other bounty hunters try to find the "ultimate power" that is said to be located in the Alimbic Cluster. He and the other bounty hunters battle Samus throughout the game, and are saved by her from Gorea at its end. His spaceship appears in the special ending of Metroid Prime 3: Corruption, which is unlocked after reaching 100% completion, in pursuit of Samus Aran. Sylux also appears in the special ending of Metroid Prime: Federation Force, unlocked if a Metroid egg is rescued in a previous mission, in which he infiltrates a Galactic Federation research station, and releases an infant Metroid from a stasis tube.

In Metroid Prime 4: Beyond, Sylux and the Space Pirates attack a Federation facility holding a mysterious artifact. The artifact sends him, Samus, and several Federation soldiers to the planet Viewros. Decoys of Sylux are fought throughout the game. In visions seen by Samus, it is revealed that Sylux is a former Federation marine and the sole survivor of his platoon after a disastrous mission, in which he wanted to capture a Space Pirate superweapon and recklessly disobeyed his superiors, getting his men killed; Samus then destroyed the superweapon as ordered, making Sylux hate Samus and the Federation. After Samus defeats him in a final confrontation, he damages the Master Teleporter, forcing her comrades to sacrifice themselves in order to allow Samus to leave the planet.

Baby Metroid