It's been a long day here, but I can't get metallness 1,0 to work.
I create a Physical Material and put metallness to 1,0, put it on a teapot, pick an HDRI. It's not metallic in Corona, but in Arnold and V-ray. Maybe this is logical because the CoronaLegacyMat didn't have metal, buuut maybe it could be mapped to the IOR in some clever way?
Any recommendation on how to make a metal with Physical Material so that it renders resonably the same in all three renderers?