Mr Kirk Hammett is a collector. “I’m a habitual collector, bro!” he says emphatically. “My friend called me the other day and said, ‘Why do you collect plastic bags?’ And I thought, ‘I’ve been completely rumbled here’ – because I do. I have OCD and collect anything. I’m at that age when I can look back on my life and see patterns when I go hard on buying certain things – guitars, vehicles, watches, horror memorabilia, comics…”

Hammett is, of course, also the lead guitarist of Metallica and considered one of the best heavy metal guitarists in the world. He joined the band in 1983, barely into his twenties, and never looked back. Having grown up “with very little”, when he found himself with some disposable income, he went large on the shopping. Watches meant an upgrade from the Mickey Mouse model he started with to Rolex sports models, Jaeger-LeCoultre Reversos, Omega Speedmasters – “I love space stuff, I love Nasa,” he enthuses – and Pateks. “Great stuff, man,” he says.

“The thing is that I really beat these things up,” laments Hammett, who is gaining credibility as a solo artist (check out last year’s EP, Portals). “My guitars look beaten up. My cars are in the bodyshop all the time. My watches have all these scratches and I’m always cracking the crystal. There’s all sorts of wonderful watches I love, but most of them just sit in my treasure box. I’ll take one out and wear it for the afternoon, but I’m always worried about it banging up against my guitar. I have to assess the situation before wearing a watch.”

If the love of fine timepieces perhaps seems at odds with macho heavy metal style – isn’t that all leather bracelets, biker boots, black T-shirts and “tough scary riffs,” as Hammett puts it, “like scraping a shovel across concrete” – he argues otherwise. And that’s not just because, he says, he’s discovered the more elegant, expressive quality of clothes over the last 15 years and tried to bring the band along with him. “Stagewear needs an element of flashiness to it, because it needs to be something you can see from 50 feet away,” Hammett says. “Wear all black – as you so often do in heavy metal – and when the stage gets dark, suddenly it’s like, ‘Where’s Kirk gone?’”

Actually, heavy metal is all about the gear, he contends – the wiring and the pedals and the dials (all the way up to 11). “And I just love gear,” he says. “With acoustic guitar, you can get away with just the instrument, a mike and an amp. For equipment options with an electric guitar, the sky is the limit. James [Hetfield, Metallica bandmate] and I have a warehouse just full of equipment.”

It’s one he keeps adding to. In his honour, the Gibson Custom Shop and Epiphone has just created a special edition of Hammett’s famed 1979 Gibson Flying V – that’s what gave such a distinctive sound to Metallica’s 1986 album, Master Of Puppets, among others. One of his most treasured possessions? The legendary “Greeny”, a 1959 Gibson Les Paul Standard, named for its first owner, Fleetwood Mac founder Mr Peter Green, before being sold to Thin Lizzy’s Mr Gary Moore.

“Some guitars are not just a guitar,” Hammett says. “They’re a vehicle for creative energy. Put it in the hands of someone and music just appears. It was destiny for me to have ‘Greeny’. When I was 15, Gary Moore’s solo album came out and there’s this photo on the sleeve of him bending back playing a note and I thought, ‘That’s an amazing guitar’ – 35 years later, I’d heard rumours [about it being on the market], so tried it. Within 60 seconds, I was thinking, ‘What’s going on here? This is not like any guitar I’ve ever played’. The sound is amazing. I told the guy that I wasn’t giving it back to him and I’ve had it ever since. I still look at it, all the dings and scratches, and think, ‘This is Gary Moore’s guitar!’”

These days, Hammett spends his leisure time on a very Zen combination of surfing, meditation and transcribing classical music into electric guitar, from his home in Hawaii. And he’s more than aware of his own legacy. He says he’s still amazed by the impact Metallica continues to have, arguing that it’s one of just a few bands that speak to people when they’re young, but to which those people remain loyal for life. But building that legacy has, he stresses, come at a cost.

“When I was a teenager and aspiring to be a rock musician, I was taken with its glamour and the romanticising of the lifestyle,” he says. “Well, then you experience it – and it’s all bollocks. Believing in sex, drugs and rock’n’roll is a quick way to ruin your life.” Hammett is proud to be clean of drink and drugs for nine years now. “Pretty much all of my peers bought into all that and some didn’t come out at the end of it – addictions, narcissism, just inappropriate behaviour, all that can change people for the worse.

“The problem is that it seemed like a good idea at the time,” he laughs. “Yes, it was fun, but every day, I have regrets [about it]. If I can make any amends, it’s to tell young musicians now not to do it. Just put the music first.”