So I'm using a Metal/Rough workflow in painter and in UE. I'm using the environment map "bonaficio aragon stairs" because its at the beach and my scene is at the beach. and lastly I pack my Roughness, Metallic and AO into one map and its definitely hooked up correctly. Yet my metallic looks completely black in UE. Here it…
I had this problem before, and here's an answer that worked for me. https://forums.unrealengine.com/development-discussion/rendering/28835-substance-to-ue4-issue-black-metal-in-ue4-viewport
Are you using the packed export preset? Filtered the metallic channel (blue) to the metallic input in the shader? Disabled sRGB on the texture? Questions like this should go in technical talk section.