Upload & Sell: On
The right kind on B&W content can be quite great on metallics. The principle is, in my opinion, that the reflective deep metallic layer is only revealed when what overlies it (pigment ink) is of reduced opacity. Given that heavy deposition of pigment ink would be pretty opaque, but that light ink deposition is of reduced opacity, one finds the most "metallic drama" in high hey areas. The papers, as an aside, do seem to offer decent Dmax and gamut, unrelated to metallic character. So the right image can render with good combinations of color pop, blacks, and the appearance of depth that relates to the areas where less pigment is laid down.
The above Luminous Landscape thread offers a better discussion of this than I'm able to, in case you are interested.