Mother Brain is perhaps the most interesting fight of the game as she will fight you in two phases, the first of which is a throwback to classic metroid on the NES.
Mother Brain is the final boss of the game. Mother Brain is a recurring antagonist of the Metroid series, and a major leader of the Space Pirates. MB1 rests within her glass tank.

She has three phases, which are usually referred to as MB1, MB2, and MB3.
MB2 rises from the ground into a mechanized body, fought before acquiring Hyper Beam. She appears in Metroid (and its remake Zero Mission), Super Metroid, and in a flashback sequence in Metroid: Other M. In Metroid, Samus had to fire missiles in the opening of Mother Brain's Control Capsule while avoiding enemy Rinkas.