Metallica has joined forces with Lou Reed, and together they are "90 percent" finished recording an album featuring 10 new songs written by Reed, with strong arrangement help from his new headbanging buddies. 

According to Rolling Stone, the New York City-based singer-songwriter and the California metal legends hit it off when they performed two of Reed's classic songs together at the 25th Anniversary Rock and Roll Hall of Fame concerts in 2009. Apparently, they got the idea to work together pretty quickly: "We knew from then," says Reed, "that we were made for each other."

At first, the unlikely team's plan was to re-record a collection of the elder statesman's lesser-known tracks, but Reed instead presented Metallica with songs he'd written for 'Lulu,' a German theatrical show currently running in Berlin. "It was scary at first," recalls singer James Hetfield, "because the music was so open. But then I thought, 'This could go anywhere.'"

Reportedly, the music that resulted is an unlikely but undeniable combination of the creative peaks of both band's recorded output. The track 'Pumping Blood' features drone, march, and speed-metal sections, and was cut in one take, while 'Mistress Dread' sets Reed's monotone voice against a "relentless staccato riff."

A few months back, Metallica announced they were going into the studio to record something they labeled not "100 percent a Metallica record," but we just assumed that meant another entry in their 'Garage Days' cover album series.

Instead, this collaboration looks to have broken new ground for everybody involved. Neither Metallica nor Reed are currently tied to a record deal, and there's no title or release date for the album yet.

However and whenever this record comes out, it should be, at the very least, one hell of an interesting listen.

Watch Metallica and Lou Reed Perform 'Sweet Jane' Together