Using metals in sketchfab I made a chair that has a procedural cycles leather texture. I`d like to bake this texture and set my model to shadeless rendering on sketchfab. But the chair structure is metal, and I can't bake it. How do I manage this? I want to use baked textures with Sketchfab metalness. 

Maybe if I could transform my procedural texture in diffuse, normal and glossiness maps, then I could use only sketchfab textures and no need to baking them.

What's the best solution in this case? Is there a way to use baked textures with metal textures, or do I have to make maps for my procedural textures? And how do I do that?

Sorry for my english, it's not my native language
"Metal" textures are often determined by a number of different textures working together to create the appearance of metal. These can include a number of things such as Diffuse, Specular, Normals, and glossy shaders. In order to make these usable by external programs you can either bake these maps individually of create a PBR material, which is basically a combination of all of the above.

There are lot's of tutorials on how you may create PBR materials in blender my favorite as always is from Blender Guru.

However if you wish to export individual maps there is a great tutorial here on 
stack exchange.