avant roof rails (silver) - are they coated with anything?
 

or is the metal bare?

Brushed aluminum is what i think mine are.

i tryed a test with metal polish and they didn't turn black like they should have.
 

So i just used the clay bar.

If the metal doesn't turn black with metal polish like kiwi said then they are clearcoated...
 

Common for Audi to do that, protects the finish like on the aluminum mirrors.

Anodized clear
 

on my '98 the silver aluminum rails are clear anodized (not a clear coat). That is why you don't see black when using metal polish.