I have had zero issues with my Coach metallics from the past several years. I did have an old Madison bag in gunmetal that wore a bit on the corners but I abused that bag.
I don't have a bag with metallic leather, but I do have a key loop with metallic leather. I used it for a long time, dropping it, getting it wet, tumbling around in my bag with my keys, etc., and still have had no wear on the leather at all.