In her previous mission, bounty hunter Samus Aran ruined the space pirates' plans to use the newly discovered bioforms known as metroids. To ensure that the space pirates can never obtain any more metroids, the Galactic Federation sends several teams to the metroid's home planet SR388 to destroy them for once and all. However, when each of the teams disappear, the Galactic Federation contracts Samus to finish the mission.
—rayeraymusd and Brian McInnis