James Hetfield loves being in a bad mood because it improves his songwriting.
The Metallica frontman says he pens his best tracks when he is either feeling miserable and angry, or incredibly happy and waits to experience one of the mood extremes before he attempts to write new material.
He said: "I'm in a good mood I'm going to write something really great. Or if I'm in a bad mood I'm going to write something really great. Somewhere in the middle, I'll wait until one of those other emotions happens. Or if I get a really good guitar sound in the tuning room,that will spur on a great riff too"
The group a currently a year into a two-year touring schedule but the rocker insists he still finds the time to create new songs.
He added to BBC Newsbeat: "It's like a waterfall. Sometimes it's happening, sometimes it's not. When we're on the road, sometimes the ideas are flowing, you can't really turn it off or turn it on. It's constantly flowing but at different levels. And most of it has to do with me."