can anyone honestly say a band has changed their life and provide an example

Autopsy - changed my view of death metal and metal in general, it was the gateway band for me into underground death and black metal. I liked Morbid Angel before, but this was the band that opened my eyes.
 
I'm sure that in some minute way, every band I've heard has changed something about my life, whether I spent money on their CD or not, listened to them at some key time (or even just on a random summer's day) or any other mundane activity that could be very different without that one particular band of the moment.

But if you mean "has anything SUBSTANTIALLY altered perception of the world/life as we know it" or something...not really, no.
 
Black metal, particularly Emperor and Mayhem, got me in touch with the darker side of my own nature and human existence in general. That was also around the time I read the Satanic Bible and started delving into the occult. Though I am no longer a slave to the brainwashing of modern occultism, it did widen my horizons and give me a new appreciation for religion in general.
 
Can't really say that, but Van der Graaf Generator and Camel made me interested in exploring early prog rock(and related genres) beyond King Crimson and I'm quite thankful for that.
 
Morbid Angel - Altars of Madness helped me appreciate Death Metal. Then Immortals Pure Holocaust threw me into Black Metal.
 
Well, music is my life. It's changed a lot about me & opened my mind in many ways, likely even in ways having nothing to do with actual music. I've made great friends based off our similarities in music taste. At the same time music has made me not care what people think of me. My music has set me apart from all the people here who drive around blaring 50 Cent & Beyonce through their subwoofers. I only know two people here who listen to Metal, & anyone else I will play my music around at any time, regardless of if they don't like it (well, I will be nice sometimes, I'm no asshole, but I won't listen to something I hate especially while driving). When I first got into Yngwie Malmsteen he totally blew my mind & changed my approach & technique applied to the guitar. I probably was about 15-16 when I got into him. In the years to follow I broadened my tastes, & it made me a different person in a lot of small ways. I virtually spend all my free time doing things that relate to music, be it listening, watching, or playing.

I definitly think music can change your life, it did to mine. Without my current tastes I would be a different person, & so would most people here. I can tell that music plays a major role in a lot of people's lives here.
 
Certain songs have helped me through depressing times, but hard to say if the outcome of my life was drastically changed by that.
 
I'm not sure any bands have had any major impact on my life's course besides the bands that got me into metal in the first place (since metal is my life at the moment). Those bands are Arcturus, Borknagar, Hypocrisy and The Kovenant.
 
No, not really - music has pretty much absorbed my life, and I listen to metal almost exclusively (not intentionally, it's just what I feel like listening too), so I guess it sorta changed my life, but I don't think that counts.
 
Can music really do that?

Can anyone say "I listened to Beethoven's 5th symphony and was inspired to create a cure for cancer".

you're going a bit extreme here, but it's definitely clear that music can influence people. Look at 60s rock and 80s norwegian black metal, both big cultural influences.
 
I felt like something clicked inside me the first time I heard Master of Puppets & Ride the Lightning. And they set me on a whole new path of musical discovery which culminated in me playing in bands for many years. I don't know if I'd be the same person if I hadn't heard Metallica in 1987.
 
I kind of agree with V5 in that I'd still be the same smartass with the same general attitudes, dispositions, habits or quirks regardless of what's in my stereo. I've heard it said that most peoples' personalities are shaped within the first 4 years of their lives, and from what I can tell, most people never change in a lot fundamental ways.

BUT...everything is related to everything else in one way or another, and I could probably make a valid argument that music has shaped many of my past decisions and choices. That may at least produce some kind of short-term effects. It could be argued that that Metallica tape I bought in middle school introduced me to the metal underground and set off a chain reaction that 1) established concert-going as a regular activity 2) caused me to start a band 3) defined my social circle 4) took me on tour and a lot more traveling 5) led me into two of my relationships (and a lot of unpleasant drama), and so on. Musical tastes do not define me (or if they do, my personality defines them at least as much as they define me), but they've shaped so many of my life experiences, and that probably counts for something.
 
i mean like this:

youre a big iron maiden fan so you hop on a plane and fly to a nearby city to catch a headline show. on the plane you meet someone who turns out to be your future wife (or husband). if you didnt like iron maiden you wouldnt have been on the plane going to the concert thus not meeting that certain person.

the above is an actual true story, btw.