Metallic paint requires a bit more solvent, but not much. Theres more of a difference between a gloss and a flat than there is between a gloss and a metallic.
Water and acrylic paint wont really give you a "real" paint high either, you need the industrial stuff that requires a 250-320 bake for that.
I'm not a paint sniffer, I just worked as a quality control guy at a paint factory for a few years. Most of the stuff at walmart and lowes type places are relatively benign and wont get you "high" anyways. Its just that the amonia used to get the ph high enough to adhere well to metal in combination with the alcohol thats usually used as the modern primary solvent in combination with the aerosol from the can.
Most of the old school chems that made paint huffing famous have been phased out of use in favor of safer alternatives. It would technically be safer and just as effective getting high from inflating a balloon or condom with keyboard cleaner and huffing that.
Its a stupid and uncomfortable high anyways. I've been through a couple of substance abuse programs, and not once have I ever ran into anyone whos ever even mentioned huffing.