Bay Area thrash veterans Metallica were not invited to perform at this year's Super Bowl halftime show, though they're probably San Francisco's most commercially successful hometown act, and frontman James Hetfield doesn't think they'll ever rock a Super Bowl halftime.  In an interview with the Associated Press, Hetfield explained that Metallica's style, while it has developed a widespread fan-base, does not match the typical entertainment seen at those events.  "We're not a variety show. We're not pop. We're not sparkly and all that kind of stuff that I think seems to be what is needed for that," the singer explained.  Check out Hetfield's comments about Super Bowl halftime shows in the YouTube clip below.  Despite not performing at halftime, the band was a huge part of Super Bowl weekend, serving as the headliner for last night's "The Night Before" concert, with Cage the Elephant.  Held at AT&T Park, the concert was webcast so that fans around the world were able to watch.