METALLICA / LADY GAGA duet . . . SHOULD HAVE rocked. And it did, except for one thing: JAMES HETFIELD's microphone didn't work for the first few minutes. He and Gaga were supposed to be trading verses, but his audio was non-existent. So it came off really bad until they fixed it. But the band rocked, and Gaga rocked . . . and she showed her belly again, so suck it, haters. After it was over, James was so pissed, he threw his guitar offstage. For a lot of Metallica fans, it brought back the OUTRAGE of the '89 Grammys, when Metallica lost the inaugural Hard Rock / Heavy Metal Grammy to JETHRO TULL.