The player controls the bounty hunter Samus Aran, who protects the galaxy from Space Pirates and other malevolent forces and their attempts to harness the power of the parasitic Metroid creatures.

Metroid combines the platforming of Super Mario Bros. and the exploration of The Legend of Zelda with a science fiction setting and an emphasis on nonlinear gameplay.

[3] The series is notable for its non-linear progression and solitary exploration format where the player only controls Samus Aran, with few or no other characters to interact with.

[3][6][7] Hirokazu "Hip" Tanaka, composer of the original Metroid, has said he wanted to make a score that made players feel like they were encountering a "living creature" and had no distinction between music and sound effects.

[6][8] The only time the main Metroid theme was heard was after Mother Brain is defeated; this is intended to give the player a catharsis.

[9] The Metroid franchise takes place in a science fiction setting where humanity is shown to be a part of a spacefaring sovereignty known as the Galactic Federation.

Other races are both a part of the Federation as well as close allies, the most prolific being the Chozo, an avian species possessing advanced technology and skills in bioengineering.

They are led by the dragon-like warlord Ridley, and plot to develop weapons of mass destruction from hazardous life forms and materials to destroy the Federation and secure galactic dominance.

The eponymous Metroids are a species of predatory, jellyfish-like organisms that feed on an undetectable life energy found in all living creatures.

Most of the games center around the efforts of various organizations, including the Space Pirates, the Galactic Federation, and rogue members of the Chozo race, to weaponize the Metroids and the subsequent conflicts they cause.

She serves in the military of the Galactic Federation before departing and beginning work as a bounty hunter,[14] while facing the forces of Ridley and Mother Brain.

[14] In Metroid Prime, Samus travels to Tallon IV to stop the Space Pirates from exploiting a Phazon-infused meteor that has poisoned the local ecosystem.

[13] After battling a cybernetically enhanced Ridley and clearing out the Space Pirate presence on the planet, Samus purges the Phazon from Tallon IV by defeating the titular enemy, a Phazon-infected Metroid.

Metroid Prime: Hunters, which is unconnected to the Phazon storyline, sees Samus respond to a distress call to the Alimbic Cluster.

[13] They team up against many bioweapons created by a Federation science group, including clones of creatures Samus faced on Zebes like Ridley and the Metroids.

Samus is sent to the planet herself after contact is lost, coming into conflict with the X and a Chozo war criminal named Raven Beak, stopping both from invading the rest of the galaxy.

[3] Metroid was designed to be a shooting game that combined the platform jumping of Super Mario Bros. with the non-linear exploration of The Legend of Zelda and a darker aesthetic.

[3][21] Ridley Scott's 1979 science-fiction horror film Alien was described by Sakamoto as a "huge influence" after the world of the first Metroid had been created.

The development staff were also influenced by the work of the film's creature designer H. R. Giger, finding his style to be fitting for the Metroid universe.

Metroid II also further established Samus' visual design, with the bulky Varia Suit upgrade and different arm cannons.

[42] In 2004, Nintendo also released Metroid Prime 2: Echoes, which sees Samus switching between parallel light and dark worlds and introduced more difficulty.

[33] Metroid Prime 3: Corruption, released for the Wii in 2007, added motion controls[3] and has Samus exploring separate planets, with more emphasis on shooting action.

[4] Samus Aran was recognized by Guinness World Records as "enduringly popular"[2] and as the "first playable human female character in a mainstream video game", although Toby Masuyo ("Kissy") from Namco's Alien Sector predates her by one year.

[118] In its debut week in Japan, Metroid Prime 3: Corruption sold 32,388 units, ranking it behind Ryū ga Gotoku Kenzan!, Super Smash Bros. Brawl, Wii Fit, and Gundam Musou Special.

Other notable Metroidvania games include Cave Story (2004), Shadow Complex (2009), Ori and the Blind Forest (2014), Hollow Knight (2017), and Chasm (2018).

[104] Ridley's clone from Metroid: Other M appears as a boss on the Pyroshpere stage in Super Smash Bros. for Wii U, where he will join a fighter's side if they manage to knock him out.

Various other characters such as Metroids, Mother Brain and Dark Samus appear as either trophies or stickers in the Super Smash Bros. series as well.

[150] In Japan, a Metroid manga series was published in Kodansha's Monthly Magazine Z beginning in November 2003, and ran for 16 chapters which were later collected into two Tankōbon volumes.

[5] The director John Woo acquired the rights a few years later,[153] and his studio Lion Rock Productions was to produce and release the film before 2006.

[155] In 2013, Sakamoto said he could support a film directed by Ryuji Kitaura, the director of the CG scenes in Other M, if the concept and methodologies were good enough.