with all due respect to metalheadz, for they are a great band, i dont think they ever did justice to metallica songs, at least vocally. which is why i dont think any band can ever pull of a good metallica cover. nobody sings like hetfield. not even hetfield himself anymore.
that being said, would love to hear sad but true, harvester of sorrow, and blackened. off the top of my head, i think theyre the most vocally demanding of metallica's songs.