People dont grow out of metal, they just never grew into it. If they did put on something, it was only to fit in with a particular group.
Or unless they're retarded or american and think Linkin Park and Korn and Slipknot were metal, and they were into it, because they heard Freak on a Leash, Before I forget and some LP song and didnt dislike it.
If you truly get into bands like Sabbath, Maiden, Priest, Met&Meg and those, it's for life and for sure. You may branch into other genres like grunge and rock and blues and folk, you may cut the hair and ditch the black jeans, but Sabbath and Maiden stay with you forever.