Few people are associated with the world of Metallica as much as Bob Rock, who produced several of their albums, but most famously worked with them on their iconic 1991 self-titled record. The producer has once again looked back on the experience, noting that the band were "suspicious" of everyone, and "intense" to work with.

“Metallica are not wimps,” Rock recently told Metal Hammer. “They believe that they’re the best band in the world, and everyone else needs to get out of the way.”

The band had initially approached Rock about mixing the album, and he turned down the offer, as he was also presented with the opportunity to work with Bon Jovi's Richie Sambora on a solo album. However, he ultimately made the decision to go with Metallica — but he wanted to produce it, not mix it.

"Metallica didn’t trust outsiders,” the producer remarked. “Not just me, they were suspicious of everybody. I can say that I’d never been involved with people who were as intense as them.”

Throughout the eight-month-long project, Rock noted that many tensions arose, especially as a result of he and the band members challenging each other.

"Making an album can be an intense experience," he admitted. "You’re thrown into a room with other strong-willed, creative people for months and months and you have to find a way to listen to each other and make it work. I never said, ‘No, you’re wrong.’ I just showed them other ways to potentially get what they wanted.”

However, he noted that such disagreements and tensions helped some of the most legendary bands in rock 'n' roll history — such as The Rolling Stones and Aerosmith — to create their masterpieces.

"It’d be kinda boring if everyone did everything you suggested!” he concluded.

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