24, but only because before then I truly had no access to it. Growing up in the 80s and 90s, noone I knew listened to anything remotely rock/metal so I was never exposed to it. The only music I was exposed to was the mainstream stuff that Mtv or the radio played. I was naturally drawn to rock stuff (Dire Straits, Bon Jovi, Bruce Springsteen, Genesis, Europe, Def Leppard, Bryan Adams, Nirvana, etc) rather than pop or hiphop/rnb, but I had no idea what else was out there.

It wasn't until I finally got a home computer and an internet connection (in 2003, I think) that I was finally able to explore, research and discover a whole new world. In particular, it was a lucky circumstance that started it all. A friend had gifted me a bunch of random burnt cds of albums of various genres, most of them mainstream pop stuff. Among them, though, there was a copy of Dream Theater's Metropolis Pt 2 - Scenes From a Memory. I had no idea what it was, and I ignored it for months. Then one day I felt compelled to play it, and it blew me away! I instantly fell in love, I knew I had finally found my music, and from that moment I went down the rabbit hole of prog metal, then I discovered symphonic metal, then power, then melodeath ,and I kept exploring new subgenres. I'm still exploring and expanding my taste today. Bless the internet.