Actually, if you ever listen to interviews with him, he sounds intelligent and makes a lot of sense. A good example of why we shouldn't judge a book by its cover. And he has been advocating conservative views for a long time.
Surprisingly many heavy metal (or death metal) bands have very educated members, many of which may have a Masters in Musical Theory. I guess they just love that kind of music.
I would expect a group like Megadeth to support Ron Paul more than anyone else as many metalheads are big supporters of anarchy (or are at least very libertarian) and he’s the closest thing to that.