The Fusion Suit is a form of the Power Suit worn by Samus Aran in the Metroid series, specifically in Metroid Fusion. This suit is an unintentional byproduct of the surgical removal of the Varia Suit's outer plating and subsequent injection of Metroid DNA in order to save Samus' life from a life-threatening infection of X-Parasites. A radically different design for the Power Suit, the Fusion Suit--due to the Power Suit's biomechanical construction--has an organic appearance, featuring blue muscle fibers and tendons laid over a thin yellow plating, the helmet's breathing tubes being diverted into the collar, an enlarged, blue visor, and three small blades protruding from the underside of the left forearm.
As it is the Power Suit stripped of all outer plating, the Fusion Suit's defenses are initially lacking. It has almost no shielding against attacks and cannot insulate the now part-Metroid Samus from extreme cold, though these are remedied upon acquiring suit upgrades. However, the suit does allow her to absorb X-Parasites to gain health and ammunition, due to Metroids being the sole predator of the X. The reduced weight also allows Samus to easily hoist herself up onto ledges, a feat that was previously impossible without outside influence.
In Metroid Dread, the Fusion Suit is shown to have partially regenerated its armor plating, due to the blue tendons and muscle fibers peeking out from between the plates.