Short for Avenged Sevenfold
a - avenged
7 - seven
x - fold (times)
A newer band that combines hardcore, punk and metal. One category they're often put into is "Melodic Hardcore". Two albums - Sounding the Seventh Trumpet and Waking the Fallen. Extremely poetic, deep, rich and beautiful lyrics. Sick, fast-paced drumming. Long, epic, well-planned out songs. An incredible band all-together.
Songs to check out: Unholy Confessions, Chapter Four, I Won't See You Tonight Pts 1 & 2. Those are all from Waking the Fallen, which I'd say is the better album.