The game takes place between Super Metroid and Metroid Fusion. Other M opens with a cinematic showing the final battle with Mother Brain at the conclusion of Super Metroid. After escaping the exploding Planet Zebes, Samus Aran awakens on a Galactic Federation ship. After leaving, she receives a distress signal, commonly coded as "Baby's Cry", from a dormant "Bottle Ship", which is floating a short distance away from a Federation vessel.
Gameplay is designed to allow switching between first person and third person views based on how the Wii remote is held. Environments are 3D, and Other M is the first game in the franchise to feature melee combat.
Source: Wikipedia, "Metroid other m", available under the CC-BY-SA License.