I used the rock symbol / Sign of the Horns in some of my marketing for my month of MUSIC, because I like rock music. And it went really well with showing off the rings. But I've been using the sign for years.
(Tailgating at Coachella 2007)
But where did it come from?
According to Wikipedia, the hand gesture was first depicted by Buddha in India around 500 BC as a sign to ward off evil spirits or obstacles. That idea continued in parts of Europe, where it was thrown at the mention of unfortunate events as protection against bad luck. This all sounds pretty legit.
Now the first time it was depicted in music was, surprisingly, by John Lennon in 1967 on the album cover for a Beatles single. And I said "surprisingly" because it is so intertwined with rock and heavy metal music. In that genre, it was the occult rock band Coven that first used it on an album cover in 1969, along with a depiction of practices of the dark arts. (Snape?)
It became more mainstream in metal thanks to Ronnie James Dio. The story goes: when Dio joined Black Sabbath in 1979, he followed in the footsteps of Ozzy Osborne. Osborne had used the peace sign at every show to connect with fans, and Dio wanted something similar. He remembered the sign his Italian grandmother had used to ward off evil spirits, so adopted it on stage. And there you go. Pretty cool, huh? (Did notes in an interview that he doubts he was the first one to throw it in rock, just that maybe he made it more popular).
I listen predominately to rock music, so I have no idea if the sign is used at pop concerts or electronic concerts? The symbolism is good no matter where you are but to me, it will always mean to rock on.
(Thanks to Wikipedia for all of this)