Hetfield tells the Village Voice: "It’s absolutely crazy. That was the song I thought was least Metallica, least likely to ever be played by us – the last song anyone would really want to hear.
"It was a song for myself in my room on tour when I was bumming out about being away from home.
"It’s quite amazing. It’s a true testament to honest and exposing yourself, putting your real self out there and taking the risk; taking the gamble that someone’s going to step on your heart with spikes on, or they’re going to put their heart right next to it. You never know until you try."
He says discussion over recording the track "solidified" his attitude to it. "We were doing the right thing, writing from the heart about what we felt, and you can’t go wrong that way.
"It’s become an unbelievable song live, and from the New York Hells Angels putting it in their movie to sports people, to people getting married to it, people relate to it.
"I’m grateful that the guys forced me to take it out of my tape players and make it Metallica."
Hammett is the subject of various gags in the documentary "A Year And A Half In The Life Of Metallica", referring to problems he’d experienced with "Nothing Else Matters".
The guitarist explains: "We kept putting it in the set and taking it out until we were actually able to play it. I had to relearn that whole intro part to play by myself on stage – which was a little bit intimidating for me at that point. We never had a song that started that way.
"After a while, once we got down it down, it was no problem. Once we put our sights onto whipping a song into shape and getting it together, we’re pretty good about making it happen."
Asked whether he ever feels like dropping the band’s signature track "Enter Sandman" during a live show, Hammett says: "There’s a certain amount of songs we know we have to play. The great thing about out music is most of it is really, really fun to play."
But he adds: "There were times when the mention of 'Seek And Destroy' would make me gag – but we started playing it in a heavier key and now it sounds like a brand new song to me. I love it all over again."
Metallica recently hailed their Orion Music + More festival a success, and have released a video recap available below. The band are beginning to think about work on a new album. Hetfield has said he’d like it to appear next year, but he doesn’t know whether it will work out that way.