I was 13 or so when I discovered Sonic Youth... A battered copy of Goo appeared in my brother's bag when he unpacked after a trip to Spain, and I never looked back.
I think partly why I love them so much (beyond the fact that they are fucking awesome musically) is that at the time I discovered them I was pretty insecure, I didn't really know who I was and I was total confused about what was 'cool' and how people perceived me (I was a 13 ye old girl!). Then I listened to this music and no one I knew had really heard it or cared about it, and I couldn't pin point it anywhere, so listening to it didn't make me preppy, or a skater or a goth or any of those stupid labels that teenagers have. I loved the fact that Sonic Youth were actually a band that did what they wanted and didn't give a fuck, not just a band who said they did what they wanted... and I guess that kind of made me realise that being cool is just being yourself and happy with who you are.
And then everyone started to love me
only kidding, I guess what I just said was corny and trite but I simply mean that SY taught me how to be myself a lot longer before I would've figured it out for myself.