What you've heard is true. Metallica and Lou Reed have made an album together. I mean this in no way to sound condescending, but if you are not a musicologist, or at least well versed in the complete history of rock, you may not even know who Lou Reed is. He was the founder of the Andy Warhol era pre-punk band Velvet Underground, and as a solo artist had a big 70's radio hit called 'Walk On The Wild Side'. I own a couple of Lou Reed albums on vinyl, and I can honestly say his collaboration with Metallica is one oddball pairing. It's even upset a few folks, like the Fuhrer, as you can see in the accompanying video!  Warning, the subtitles in the video are full of VERY EXPLICIT LANGUAGE!