How to do this???

Dear All,
I’m making an fps game and currently I’m at the texturing part.
I have a skeleton mesh modeled and rigged in Maya.
I wish to know how to lay out the uvs so I can texture it in MARI? Note: I know - more or less - how to lay out uvs. the question is not that, but the following:
There are some parts that are metallic (it is a cyborg of a sort) and other parts are not. I planned to use two separate materials for it and plan to texture accordingly.
Can I use two materials on one skeleton mesh? Shall I merge my object into one before UVing then exporting the obj for texturing? How do you usually do this?
Or just one big object that shares the space meant for the uvs then use a mask in UE for metallic property? (mask in painted in MARI as well)?
This is literally the first time I’m doing this.
I’m sending you a quick mental ray render, no textures etc whatsoever, just a simple lambert. It is built up from a LOT of objects and I do not know how to pull this off.
Thanks in advance.

I’m not a MARI user, but the general solutions would be to make use of material ID’s or generate a material ID mask.

I believe the material ID mask shows UE that e.g. the white parts (mask painted in MARI in my case) are getting the effect from this material, the blacks are not?
Also, if I were to use one mat, I can use a black/white mask to show UE the metallic and non metallic parts, right?

yes you can.

thanks for the update.
Then I can do it all with one material. The only thing I do not know that exporting in one piece would be the way to go (in maya combine all into one then lay out uvs without overlap then export the obj) then texture in mari? It is not clear that can a skeleton mesh be built up from multiple objects (multiple uv sets as well) but use the same material and work as one skeleton mesh when using the animations?