This is probably as good time a time as any to mention that I identified as a rocker/metalhead as a teenager (for what it felt like an eternity, but was probably only 5 years or so).
I definitely had a classicist sensibility. The all-time greats were the triumvirate of Zeppelin, Sabbath, and Deep Purple; then came Iron Maiden, Judas Priest, and the 80s thrash icons (Metallica, Slayer, Megadeth, Anthrax, etc.). I generally favored 70s/80s heavy metal and hard rock (think Motorhead, Rush, AC/DC, Aerosmith, early Queen) and then-contemporary heavy melodic stuff (Blind Guardian, early Nightwish, Rhapsody, Angra, Dream Theater). I couldn't quite crack into death metal (because of the vocals) but I dabbled into the some of the more obvious black metal groups (Dimmu Borgir and early Cradle of Filth, both of which most black metal fans seem to disavow/detest).
Then I moved to the United States, and my circle of friends here had a much different musical sensibility (tangent: I feel like there are two different, parallel "metal universes": the Europe/Japan/Brazil axis, and the United States all on its own). I eventually tried out music I had previously refused to even consider when I was a "true metal" cultist.
I can even point to the specific album that changed my perspective of what heavy music (or music in general) could be: Nine Inch Nails' Pretty Hate Machine. Before I heard that album, I irrationally hated anything that involved electronic influences. But a friend pushed that album on me (knowing I was an angsty teenager who could totally relate to Trent Reznor's lyrics), and after that it became more difficult for me to stick to my preconceptions about music (that said, you could still catch me at age 30 saying preposterous shit like "I hate jazz").
Now, all of this was pre-Napster/MP3s (and obviously YouTube/streaming). I think there is some truth to the idea that music fans have been more open-minded over the past 15-20 years or so. I wonder if the reason why music listeners were close-minded in the past was actually to protect themselves (from spending too much money on CDs/records). I know that can be hard for younger folks to conceptualize, but mere access to music was a really valuable commodity up until the early 2000s. I couldn't tell you how much money I spent (out of what little money I had) on music that I had never listened to or artists I had barely heard of. We really have it easy these days.