Luthiers have used all sorts of non-traditional materials to produce guitar bodies. Epoxy resin, plexiglass, carbon fiber and even stone. The materials used in the construction of a guitar have always had a big impact on its tone. The species of wood in a body or neck can have a dramatic impact on the instrument's tone. As a result, creative guitar-builders have often experimented with unusual materials to create unique sounds. Metal, particularly steel and aluminum, have become a popular medium with several builders.
National Resophonic Guitars
National's resonator guitars were the first "resonator" models, produced since the late 1920s. Their elaborately chromed and polished bodies are often used to represent traditional blues music. One of their intricately engraved resonators appears on the cover of Dire Straits' album "Brothers In Arms." The resonator component is essentially a sympathetically resonant speaker, meant to increase the acoustic volume of the instrument, allowing them to play along with other instruments without being drowned out. Their croaky, metallic tone is often used in blues and bluegrass music, particularly for slide playing.
Liquid metal produce a number of electric guitars with solid-metal bodies. They use highly advanced modern engineering techniques to accurately cut and shape the bodies, before polishing them to a high-chrome shine. Their website states that their primary reason for the use of metal is the "pure," glass-like tone that the bodies produce. They're cut from solid pieces of 6061 T6 Aircraft-grade aluminum but the have produced limited editions in unique metals, for instance the GGG #001, which is covered in 18-carat gold.
Trussart guitars use a wooden neck, attached to hollow steel bodies. Trussart's creations feature distinctive corroded finishes, achieved by leaving the body exposed to the elements for several weeks before being treated and coated. The bodies also include "perforations," inserted panels of mesh that act like "f-holes" on a traditional wooden guitar, projecting more of the resonant sound.
Most guitars that use metal in their construction use it in the body. The necks generally use a traditional wooden construction to retain a familiar feel in the player's hand. Travis Bean guitars, manufactured from 1974, used a piece of machined aluminum for the neck. It's attached to a traditional wooden body. Though Bean's original intent was to improve over the stability of wooden necks, they noted that the aluminum necks provided increased sustain and response, along with percussive tonal qualities.