The first bands I remember listening too are what my dad used to play in the car. Old Genesis (before the commercial crap), The Who, Eric Clapton, Peter Frampton, Dire Straits, The Stranglers... etc. I never really paid attention to popular music, only hearing stuff that was played on Virgin Radio (also in the car and on MW with shitty sound quality).
Only when I got to about 13/14 years old did I start listening to popular chart music, dance music... basically a load of shit really.
When I reached the age of about 15 however I bought Manic Street Preachers - Holy Bible, this was the first album I ever bought for myself. I enjoyed that for a short period. I moved away from all that popular chart music at this point.
Then sometime during my 15th year I got into stuff like Linkin Park, Papa Roach and all that shite... meh. I left school and during the summer holiday of 2001, before going to college I got into Static-X, System of a Down and Disturbed. Over a period of about 2/3 years I didn't really progress much and only listened to a very small amount of bands. Killswitch Engage, Coal Chamber and Demon Hunter were a few names but there weren't many others.
In late 2003 I decided I'd almost had enough with the American shite metal and tried out In Flames. I'd heard of them 2 years previous but never really checked them out (I'd liked what I heard but for some reason at the time I didn't really have the means to get into them). In early 2004 I got into Children of Bodom's older stuff and I still think to this day it's their only good work. I also had a period of listening to Pantera and Machinehead around that time but it was only short and I soon left my American music ways.
From mid-2004 until now I've built up my knowledge of melodic metal of all varieties (mostly with harsh vox). I had a short period of listening to gothic metal in late 2004 but that didn't last long. In early 2005 I got my first taste of folk/viking metal with bands such as Ensiferum, Korpiklaani and Finntroll, I still listen to these types of bands today.
I now listen to around 300 bands, my favourite bands being Hypocrisy, In Flames (before the R2R album), Wintersun, Ensiferum, Moonsorrow, Windir, Kalmah, Skyfire, Dark Tranquillity, Bloodbath, Falkenbach, Insomnium, Norther, Korpiklaani and Finntroll.
Edit: Oh and I forgot to mention that I've recently been getting into old school swedish (style) death metal... early albums from bands like Entombed, Dismember, Unleashed, Grave, Gorefest etc.