The NT-1, like all its predecessors save the Mark V, is mechanical in origin, but is unique in that it uses mechanical parts & in this case, nanotech — to replace and mimic biological functions from the level of cells to skin, muscles, bones and organs. Since the unit as a whole has no rigid form, the NT-1 can transform.
Its default appearance is that of a six-foot (1.8-meter) tall androgynous humanoid with golden skin. However, it's capable of mimicking the form and function of anything of equal mass, whether that be furniture, motorcycles, animals, or specific individuals. In theory, they could replicate a gun, but unless they had an outside source of bullets, each shot fired would shoot a segment of their own mass. The synthetic skin is capable of mimicking any colour. While not detailed enough for a chameleon-like "cloak," one could become entirely black in order to sneak around at night.
The nanotech components have quick-release bonds, set to activate when a critical level of force is applied. This allows the NT-1 as a whole to absorb gunshots or melee attacks without significant effect.