The mental ray material lets you create a material specifically for use by the mental ray renderer. The mental ray material has components for the surface shader, and for the other nine optional shaders that make up a material in mental ray.
Material/Map Browser > Materials > mental ray > mental ray
Note: The mental ray material appears in the Browser only if the active renderer supports it.
Attention: You must assign a shader to the material's Surface component. Otherwise, the mental ray material will not be visible when you render.