Metallica guitarist Kirk Hammett spoke in an interview by Radio 21. He explained that how they came together as Metallica and how “their anger” kept them together. He said:

“I can say this with absolute authority – I have a lot of anger in me. I know James has a lot of anger and I know Lars has a lot of anger.

And I know as a matter of fact that my anger – my roots, how I was brought up, my childhood wasn’t that great, it made a well of anger inside my soul. James – same thing; Lars – same thing, a lot of anger.

When we got together, we were four angry, angry young men. What brought us together was the way we played – with anger, with aggression, distortion, energy, rawness…

He continued:

“We found each other and we saw within each other a similar anger, and that’s why we gelled, that’s why we came together.

On an emotional level, that anger never really goes away. People learn how to process it, they learn how to work through it, work with it, or just tamp it down, you know, ‘It’s not there! Not there anymore! I’m not angry! *glug glug glug*’

So it never really goes away, you just learn how to deal with it. For me, that well of anger, I can tap into it any time in any sort of situation. And it’s really helpful when I tap into that anger when I’m playing guitar, particularly guitar solos.

Even the way I play is very aggressive – my right-hand technique is really heavy, I use a really hard pick, I pick the notes really heavily and I beat up my right hand because I’m always hitting my guitar and slamming it.

It’s a therapeutic thing for me to play guitar because it helps me process that anger that’s just always there. So on a creative level, it’s really easy for us to be angry. It’s harder for us not to be angry.

Click here to entire interview via Ultimate-guitar.