A steel guitar is any guitar played while moving a steel bar or similar hard object against plucked strings. The bar itself is called a "steel" and is the source of the name "steel guitar". The instrument differs from a conventional guitar in that it is played without using frets; conceptually, it is somewhat akin to playing a guitar with one finger. Known for its portamento capabilities, gliding smoothly over every pitch between notes, the instrument can produce a sinuous crying sound and deep vibrato emulating the human singing voice. Typically, the strings are plucked by the fingers of the dominant hand, while the steel tone bar is pressed lightly against the strings and moved by the opposite hand.

A resonator guitar or resophonic guitar is an acoustic guitar that produces sound by conducting string vibrations through the bridge to one or more spun metal cones (resonators), instead of to the guitar's sounding board (top). Resonator guitars were originally designed to be louder than regular acoustic guitars, which were overwhelmed by horns and percussion instruments in dance orchestras. They became prized for their distinctive tone, and found life with bluegrass music and the blues well after electric amplification solved the problem of inadequate volume.