What is heavy metal? For some people, that topic that can generate more controversy than religion or quarterback Tim Tebow . Over the years, metal has split into more genres and subgenres than we have room to list here. Bottom line: We say you know heavy metal when you hear it. Now that that's settled, here are some pretty tame pics (and hair and clothing choices), that our friends at Snakkle.com dug up for us, of some of the heaviest rockers out there before they were music legends.