Most mucicians can be converted to Paul if you know how to phrase it.
For Nevermore, I just say stuff like "End the war on drugs! Support Ron Paul!" and they love it!
For Megadeth, just "End the UN, support Ron Paul"
You could probably even trick punk bands that Ron Paul is the anarchy candidate! (And he is, if you consider freedom closer to anarchy than fascism/socialism/military state... whatever the crap we're getting)