A hand gesture used by metal heads to symbolize their love of the music. First used by Ronnie James Dio during his years in Black Sabbath, during the Heaven and Hell tour.
Dio would use the horns to emphasize a particularly dark moment. The moment had to deserve the horns. Dio himself did not invent the sign, the horns were originally an italian gesture that was used either to repel or to give the evil eye, and went by the name Mano Cornuto. Dio gives the credit to his grandmother for impressing the horns upon him, for she was the one who used it the most around him.
It pisses me off that people give the horns at fucking Hannah Montanna concerts. They are ment for METAL.