The unlikely pairing of the metal band and the avant-garde former Velvet Underground frontman has resulted in a ten track disc which Lou describes as "a marriage made in heaven."
The album was recorded in a series of sessions at Metallica's studio near San Francisco, and features songs written by Lou, with arrangements and musical direction from 'The Day That Never Comes' group.
Lou told Rolling Stone magazine: "I knew it from the first day we played together: 'Oh, man, this is perfection, right in front of me.'"
Metallica drummer Lars Ulrich said their collaborator brought his spirit of freedom and improvisation which helped them break boundaries during the sessions.
He said: "I don't think we've ever felt this free. There's nothing that's totally outside of the boundary for us, nothing that feels like 'Oh, what happens if we go there?' It feels like we cannot land on a wrong place."?
He said:"They're bringing Metallica, with all that power. And because they're pretty sophisticated, wherever I go, they're still with me."
Metallica and Lou first worked together in 2009, when the band backed the singer for a performance of two songs in New York.
Although their collaborative project does not have a title yet, two of the songs are named 'Pumping Blood' and 'Mistress Dread'.
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