I don't think there is a correlation between intelligence and listening to metal, but the brighter someone is, the more likely that they will produce good music, or be more outspoken about metal, thus it appears that the genre is full of high intellect people. Dumb people who make bad music don't get anywhere, and people who aren't welcomed on message boards tend to leave quickly. Then again, smart people can get turned off by boards of overwhelmingly dumb people.