In a recent interview with Rick Beato, Metallica guitarist Kirk Hammett revealed that he learned how to downpick from Johnny Ramone of The Ramones. Hammett said that he was "blown away" by Ramone's downpicking technique and that he "immediately started trying to emulate it".
"I've been doing it since I was a kid, and it's all because of The Ramones and The Sex Pistols…"
The practical advantages of down-picking, in Kirk's opinion, are having more high-end and less percussion. "You must have the palm of your hand as close to the saddle as possible, but I love that sound. You can hear it in any Ramones song".
Explicitly discussing his friendship with Johnny Ramone, Hammett revealed: "I became really good friends with Johnny Ramone… He was a really, really funny guy, really a crazy, divisive character, he was a contrarian, just for his own amusement. You'd say something, he would just instantly counter it.. And, you know, I would let him have his opinions. And then I'd say, 'John, you know, you've been a huge influence on me' — I'd tell him this all the time — he goes, 'How can I be an influence on you? I said, 'The way you pick! It had an influence on so many people.'"
"And I said, 'How did you come up with that?' And he goes, 'I was just counting. That's the only way I could count, through downstrokes. It was the only way he could keep time! He was keeping time by doing just downstrokes — he practically created a whole genre of doing that." Hammett mused.
Hammett's downpicking technique has been a key part of his sound for many years and for many has has become a staple of heavy metal guitar playing. I mean, he's not James Hetfield, but you get the idea.