Lars Ulrich has compared making a Metallica album to doing a puzzle.

The 56-year-old drummer – who is joined in the band by James Hetfield, Kirk Hammett and Robert Trujillo – thinks making a record now involves taking a lot of different elements and making them fit together into song form.

He told Uncut magazine: “I look at writing a Metallica record as like a puzzle; you have 200 pieces and you have to figure it out.

“You connect them. Here's a riff. Here's a section. Here's a mood. Does he work with that guy over there?”

And the musician admitted having so many options makes him nostalgic for when their working process was much more simple.

He added: “It's nothing but f****** options - you're weighed down by possibilities, at which point you can get into romanticising the past.

“Oh, how did we write 'Ride the Lightning' in two hours? Now it takes us two hours to find the studio..."

The group have been together since 1981 but are still “hungry” for making new music and continuing to work together.

Kirk said: "We're still hungry, I'm happy to say. We have a burning desire to express ourselves. I'll go out on a limb and say as people we're highly dysfunctional and not the most well-adjusted individuals.

"However it may look, that aspect of us has never gone away and that aspect is also responsible for us writing a large amount of our music because of those emotions that brought us to become musicians in the first place, and to make sense of them."