Garage Days Re-visited? Garage Inc?? Phleeze....sure it serves a purpose for introducing metalheads to great bands like Killing Joke, The Anti-Nowhere League and the vastly superior Motorhead...but Metalica's performances of those band's material never rises above being a butchering.....and I'm being much kinder than I should be when I say that.
Like other misguided hackjobs (like say GnR's The Spaghetti Incident? ) it opens doors for those who would never otherwise hear the material.....and that's about it.