# What is the physical interpretation of Normal, Roughness, Albedo and Metalness map?

In PBS context what is the metalness map? Are my interpretation of Normal, Roughness and Albedo map correct?

I know almost for sure that:

Normal map : Models the normals per differential region in our material (kind of).

Roughness map : Together with the normal map allow to define a microfacet distribution in a differential region of our material.

Albedo map : This models the percentage of light that is diffusely reflected.

Normal + Roughness allow to define the amount of energy that is specularly reflected.

I struggle to understand the physical meaning of the metalness though, I understand it's related to have a material look like metal of course, but physically speaking I don't get what it models.