Ok I’m totally lost in translation and not sure what we are discussing, according the manual:
"The metal/roughness workflow is defined through a set of channels, which are fed to a sampler in the PBR shader as textures. The maps specific to the metal/roughness workflow are base color, metallic and roughness
About to learn basics is mandatory
But the most important is to understand first what we want to do and how it works: plastic is plastic, metal is metal…