Layered Materials, for instance, to build an individual car shader would be nice.
But the metallic paint is a layered material.
And you can apply several (solid) material types as a label on nearly all materials.
What do you try to achieve?
OK, metallic paint clearly is an oversimplified example. I would like to be able to partially reveal a second or third level of details using alpha channels for the layers on top. Think of scratches in the coating etc. or just transitions between two materials. Needless to mention much more advanced uses of layers in programs like Substance Painter of Allegorithmic.
OK - you can do this with labels on solid and transparent materials. So every label has or is its own material.
And there are several ways to achieve different effects, like scratches with some textures (raster or procedural) in roughness channel and maybe composed within nodes and tools with other textures. The material graph brings a huge amount of possibilities.
You'll find plenty of examples in the gallery, this forum and downloadable in the KeyShot cloud.
Perhaps you can start a new topic, post an example you like to achieve and I am sure that this community will help you to find a good or the best way to solve.
Honestly I am not familiar with substance painter - but seen a lot of examples from users here. So, there should be a way to transfer all the layers from substance painter to the KeyShot scene?!
Hope that helps a bit.
Cheers
Marco