Lars Ulrich on the benefits of Metallica's ever-changing tour setlist

Metallica is part of a rare breed of live acts that change up their set list each night on tour.

Drummer Lars Ulrich says the band figured out about 20 years ago that keeping its live set fresh over consecutive shows had multiple benefits.

Beyond giving some diehards reason to follow Metallica for multiple shows, Ulrich told Eddie Trunk that preparing for a new set each night helps keep the band in the moment; the shows are better because of it.

"We're certainly not one of those bands that lock ourselves down for like a month and do five days a week, eight-hours-a-day-type of rehearsal," Ulrich explained. "There are about 50 or 60 songs, give or take, that we've been playing for the better part of the last 15 years, and we can sort of roll into. Not necessarily at a moment's notice, but it's not like starting from scratch."

Layering the set with deep tracks and curveballs keeps the four members familiar with a large portion of Metallica's catalog at all times. Each night has its mainstays — "Master of Puppets," "Enter Sandman," "One," etc. — so the band can use rehearsal time to go over anything else it needs to. The performances aren't always perfect, but Ulrich says the danger of it all falling apart in front of 40,000 people keeps it interesting for everyone.

"I think anybody who knows us knows that ... we're a bit of a high-wire act," he said. "We're always 10 percent under-rehearsed."

As a result, "you feel like you're really f---ing in the moment with the rest of the guys in the band, with the audience," he added.

Metallica's recent U.S. festival appearances came with a "dare" to deliver unique shows Friday and Sunday nights, pushing the band further than it had before. Metallica was up to the task and performed two headlining sets the same weekend — more than 30 songs — without repeating a single track.

"It was super fun, but I'd be lying to you if I said it wasn't challenging," Ulrich said.