You get punk bands turning metal, but you don't get metal bands turning punk do you? Likewise you get people starting off punks and then becoming metal heads, but is it ever the other way around? It seems that once you're into metal there's no going back.
I knew guys who loved Maiden, Sabbath, Zeppelin, Ozzy, etc that went punk in 1982. So some people go from metal to punk. Then some went back to metal, so who knows.
Ha! Speaking of D.R.I and hardcore punk I just found out my friends in Sub Zero are gonna be touring with D.R.I may 15th into July... http://www.myspace.com/subzeronyc .. A shameless plug for my boys.