I made the distinction above because there is a difference between diffuse(albedo***) and base color. I can go into more detail if you’d like, but it doesn’t really matter as I think we’re on the same page now.
Correct, the metalness is typically a black and white map that essentially tells the shader which parts are metal and which parts are dielectric.
The principled BSDF is geared for the metalness workflow, not specular. However, the BSDF alone does not generate any information about the metalness of your material. Rather, you define the metalness and feed it into the metalness input. Alone, this input is 0 / black.
There are several ways you can go about creating a metalness map, but it depends on what you’re trying to texture. It’s probably going to involve some amount of manual painting, or selecting groups of polys and assigning black for non-metal, and white for metal surfaces. Or if you’re trying to achieve something like metal edge wear in blender, there are various procedural techniques.
Roughness and bump are separate, but relatable things.
A roughness map is a grayscale map ranging from 0/glossy to 1/diffuse. Diffuse objects are really just super bumpy objects at a microscopic level.
Bump handles your larger scale surface detail.
I believe there is a way to bake a bump map into your detail normals map, but I’m unfamiliar as my normals are usually coming in from outside of Blender. I’ll let someone else chime in on that front. @Secrop, you have a tool for that, don’t you? I thought I read something, somewhere.
Yes, even that is a debatable term, for you purists that care about such things.