Before I move ahead, let me say I am a HUGE fan of Metallica. I was never into Velvet Underground but I didn't dislike them either, just never listened much one way or the other.
Anyway, I was very excited about a Metallica concept album hoping for another S&M. Sadly, doesn't seem to be the case. The riffs are very Metallica and the brief parts where James sings sound good, but the song as a whole is crap. It sounds like beatnik poetry read over Metallica riffs.
So back to the title. Back in 2003, Metallica released St. Anger. As a rock album, not bad. As a Metallica album, I hated it. The drums sounded odd and there were NO GUITAR SOLOS! Not one! Now I am all for a band growing and their sound growing with them. Some of my favorite bands like Incubus and Korn sound worlds apart recently from their original sound. But those changes happened slowly. Album by album. Not 20 years of one style then a sudden shift into something completely different.
If bands want to put out an "experimental" album, I say go for it, but don't lead fans to believe it's the sound they know and love. Green Day did this by putting out an album as Foxboro Hot Tubs. Same members, different sound and style.
If you're not growing over time as a band and want to try something different, at least admit to the world that it's an "experimental" or "concept" album so we know what to expect.
