If you mean chronologically, then the order is:
Metroid/Metroid:Zero Mission, Metroid Prime/Metroid Prime Pinball,
Metroid Prime Hunters, Metroid Prime 2: Echoes, Metroid Prime 3:
Corruption, Metroid II:Return of Samus, Super Metroid,
Metroid:Other M, and finally, Metroid Fusion. If you mean by
releases, then the order consists of this: Metroid, Metroid II,
Super Metroid, Metroid Fusion, Metroid Prime, Metroid:Zero Mission,
Metroid Prime 2: Echoes, Metroid Prime Pinball, Metroid Prime
Hunters, Metroid 3:Corruption, and finally, Metroid:Other M.