Sometimes, it takes the rest of the world a while to catch up with what a handful of people know. Over the weekend, Metallica played a "secret" gig at the historic Spreckels Theatre in downtown San Diego, which seats about 1500. It was the hottest event of Comic-Con, an event that attracted well over 100,000 attendees to catch glimpses of the most anticipated sci-fi films and TV series. Among the super heroes and TV series and book adaptations was Metallica's 3D IMAX flick, Through The Never.

But back in 1983, Comic-Con was just an event catering to mostly comic book fans, decades away from Hollywood treating it like a sci-fi Sundance. The idea that Metallica would play places several times larger than the Spreckels Theatre seemed like a pipe dream.

Metallica has been such a huge band for so long, it's hard to remember how unlikely their success actually was, and how underground they were when they started. You have to go back. Way back: before their feature film, before they started their own festival, before their Lou Reed collaboration (can we just forget about that one, actually?), before their edition of Guitar Hero, before their Napster battle, before their tell-all documentary.

In 1983, the face of hard rock was Def Leppard; their Pyromania album dominated the charts and MTV. They were a New Wave Of British Heavy Metal band, but with the help of producer Robert "Mutt" Lange, they became a polished rock band who didn't sound out of place on the radio next to the Police, Michael Jackson and Duran Duran. A much glammier strain of hard rock was piquing interests of radio programmers and magazine editors: Quiet Riot's Metal Health hit #1, Mötley Crüe's Shout At The Devil and Ratt's debut EP had just come out, and Van Halen were in-between Diver Down and 1984. Those bands were based in L.A., and L.A. was what was happening.

But heavy metal has always been outsider music, and with the possible exception of Shout At The Devil, none of the above albums had much of an air of danger. A 382 miles north of L.A. in San Francisco, there was Metallica. They were not pretty. They did not sing ballads. Actually, frontman James Hetfield barely sung at all: he yelled and growled. Metallica weren't influenced by KISS or Slade; they preferred Venom and Mercyful Fate, and, above all, Motörhead. And along with bands like Anthrax, Exodus, Slayer, and Megadeth (led by exiled Metallica guitarist Dave Mustaine), they created a new counterculture within heavy metal. As drummer Lars Ulrich told authors Jon Wiederhorn and Katherine Turman in their excellent oral history of metal, Louder Than Hell, "In '83, '84, '85 the music scene in America was still dominated by the major labels. We were the big f*** you alternative to Loverboy and Journey and REO Speedwagon. At that time, we were pretty f***ing vocal about it, too. We made sure that everybody understood that we were the anti-Motley Crue."