While speaking with Billboard.com, legendary producer Rick Rubin said the group is already batting around ideas for a concept album.
"I had a meeting with Lars [Ulrich] in San Francisco . . . to explore what the focus was going to be this time around. I'm still sort of thinking about what that is going to be."
He adds, "I'll ask a lot of questions and we'll probably listen to some of the riffs that they've been writing. Usually I'll hear something that will sort of indicate the direction and then we'll talk about it from there".
Earlier this spring, the band's bassist Rob Trujillo on the new album to connect with Robin KCLB interacted with:
"Yeah. I love working with Rick. Rick, to me, he's sort of a Zen guru spirit that Metallica needs right now . . . The first album with Rick was also the first album for me, so in a lot of ways, you're kind of testing the water. Now that we're comfortable with Rick and his incredible engineer, Greg Fidelman . . . it's a great team. And it's only gonna better; I really believe that."