The term "hard rock" is often applied to many styles of rock music, their only common feature being that they deviate from pop rock, though this is generally incorrect. Two such examples are punk rock and grunge. Punk rock uses a faster tempo, less melody, fewer riffs (often using power chords), more aggression and anti-establishment lyrics.
The predominant instruments in hard rock are the electric guitar, bass guitar, and drums. The role of the guitarist is very prevalent in hard rock. Most hard rock bands comprise two different types of guitarist: lead guitarist and rhythm guitarist. The lead guitarist plays the solos, riffs and fills. Speed-enhancing techniques such as alternate picking, sweep picking and tapping, are used by hard rock lead guitarists to maximize the speed of their solos and riffs. The role of the rhythm guitarist is to complement the lead guitarist and provide rhythmic and harmonic accompaniment to the other instruments in the band. The bass guitarist and drummer's role are important to the structure of hard rock music; the bassline outlines the melody of the music while the drums sustain the rhythm of the music.