Magnet wire or enameled wire is a copper or aluminum wire coated with a very thin layer of insulation. It is used in the construction of transformers, inductors, motors, generators, speakers, hard disk head actuators, electromagnets, electric guitar pickups and other applications that require tight coils of insulated wire.

The wire itself is most often fully annealed, electrolytically refined copper. Aluminum magnet wire is sometimes used for large transformers and motors. The insulation is typically made of tough polymer film materials rather than enamel, as the name might suggest.

Conductor
The most suitable materials for magnet wire applications are unalloyed pure metals, particularly copper. When factors such as chemical, physical, and mechanical property requirements are considered, copper is considered the first choice conductor for magnet wire.

Most often, magnet wire is composed of fully annealed, electrolytically refined copper to allow closer winding when making electromagnetic coils. High-purity oxygen-free copper grades are used for high-temperature applications in reducing atmospheres or in motors or generators cooled by hydrogen gas.

Aluminium magnet wire is sometimes used as an alternative for large transformers and motors. Because of its lower electrical conductivity, aluminium wire requires a 1.6-times larger cross sectional area than a copper wire to achieve comparable DC resistance.