What is the name of the only Metroid game to feature cooperative multiplayer?

Metroid Prime: Federation Force is the only Metroid game built around cooperative multiplayer. Released for Nintendo 3DS in 2016, it lets up to four players work together as Galactic Federation Marines piloting large mechanized suits called Mechs.

Unlike the competitive multiplayer in Metroid Prime 2: Echoes and Metroid Prime Hunters, Federation Force has players operate as a team. Missions involve fighting Space Pirates, Metroids, and other threats while combining weapons, movement, and support equipment. Each player can customize a Marine’s Mech with different weapons and utilities.

The game is a spin-off rather than a traditional Samus-led adventure. Samus appears in the story, but the playable characters are Federation Marines. Another possible source of confusion is Metroid Blast in Nintendo Land, which also supports multiple players; it is a minigame featuring Metroid-inspired characters, not a standalone Metroid game. Federation Force also includes Blast Ball, a soccer-like competitive mode.