Okay, gonna try this.
Linkin Park - probably the most inportant band of my life, or at least the one that has been with me the longest. I started listening to them when Hybrid Theory came out, and I listened to them all throughout the rest of elementary school all the way through high school. My interest started to fade by junior year or so of high school, and now I can;'t say I ever really listen to LP. But I saw them last year from right near the front, and it was still awesome, and I still play Hybrid Theory and Meteora here and there for nostalgia.
AC/DC - not much to say here. The band that helped me move past bands like Green Day and other pop/rock type acts that were popular around 2003-2004. I got into all the old school classic rock and 80s rock.metal around that time, and AC/DC was the band that started it for me.
Kiss - I LOVED Kiss back in 8th grase. I had CDs, a t-shirt, and Kept the Kiss songs on repeat in Tony Hawk's Underground. I loved the catchy songs and the imagery (even though I'm not into the extravagent images anymore haha). I still have fun listening to Kiss, and I'm glad I can say I have seen them live.
Disturbed - my band back in high school. I own all of their CDs, have multiple tour shirts, and have seen them 3 times total. I have listened to them so much over the years, and was a band I shared in common with one of my better friends for years. Lots of great memories with Disturbed songs playing. Seeing Disturbed and Godsmack together at Mayhem 2011 was my high chool dream come true. I had pretty much moved past those bands by then, but that was the co-headlining tour my and my friends always talked about wanting to see.
Killswitch Engage - the band that got me into "heavier" stuff. Metalcore was the style that really introduced me to screaming/growling vocals, and helped me get into all types of heavier music. I think any metal fan in Massachusetts feels a connection to Killswitch at some point.
In Flames - the band that helped me move past metalcore and into melodic death metal. Their first few albums were the greatest things ever to me at the time, and I love all of In Flames' stuff, despite how much they have changed.
At the Gates - Slaughter of the Soul changed everything. The emotion I felt in that album was unlike anything I had heard before, and it is still one of my favorite albums of all time.
Morbid Angel - they got me into death metal, and opened the door to allow me to discover so many extreme, brutal, and fucked up bands. My favorite death metal band of all time, and Altars of Madness is one of my top albums ever.
Agalloch - Agalloch allowed me to realize that metal does not just need to be about louder/faster/more extreme. They create some of the most beautiful music I have hears, and I feel strong emotional connections to their music.
Discharge - allowed me to get into all types of other old-school punk. Discharge has such a uge influence on punk, so many bands have been directly influenced by them. I moved from Discharge to d-beat and crust punk, which is now some of my favorite music to listen to.