probably metallica, I consider And Justice For All to be the greatest metal/rock album of all time. They still sound great and I would totally recommend seeing them in concert if you can.
And Justice For All is an awesome album! Though for me, the most favorite song by them is For Whom the Bell Tolls. I just love the book and the song communicates the atmosphere so perfectly.
Nice one! I've never been to a live performance by a major band... But I have ear condition so maybe that's a good thing for me.