I had a couple of weird introductions to metal that I sometimes forget... here goes:
Back in 7th grade this Brazilian guy I randomly talked to on ICQ (remember that shit?) told me to download the song "Fear of the Dark" by Iron Maiden (this was in the days of Napster), and I loved it, but I didn't quite get into metal yet because my next musical step (after growing out of nu-metal and other assorted garbage) was punk, with a dash of Led Zep and Bob Marley, all thanks to some people I started hanging out with at that point (8th grade).
Another random introduction to "real" metal I had was as follows: Throughout junior high and into early high school I was really into the Final Fantasy games, and at some point around 8th grade I found a fan-made video which synchronized cutscenes from Final Fantasy IX with "Dark Saga" by Iced Earth. Again, I didn't really get into them until some time later, but seeing that video and hearing that stereotypical chugging, "real" metal sound was important.
Another event was being given a burned copy of We Sold Our Soul for Rock 'N' Roll
by Black Sabbath. At the time (9th grade I think) I was big into Tool and A Perfect Circle (as well as AFI), but hearing that stuff and seeing the Ozzy Behind the Music (I think that's what it was...) got me more in the direction of classic metal. I think part of what made my transition so slow was that I had some friends (the ones who got me into punk and stuff) who really hated metal (probably without much reason beyond the whole 1337 punk mindset), so I sort of hesitated to jump full-on into the genre.
Lastly there was Grand Theft Auto: Vice City. The "V-Rock" radio station really did it for me--I had heard Maiden and Priest (at least "Breaking the Law") before, but hearing those songs over and over again really got me going with the whole classic metal thing. I remember "Raining Blood" was still tough for me, I didn't like it when I first played the game.
Anyway, after that it was mostly the internet which provided me with new metal to hear. And the rest is history... that was longer than I expected, I wonder if anyone will read it.