Metal detectors use electromagnetic induction to detect metal. In addition to being used by hobbiest looking for gold and man made relics, they are also used for the detection of land mines, the detection of weapons, geophysical prospecting, archaeology, and treasure hunting.

A metal detector consists of an oscillator producing an alternating current that passes through a coil producing an alternating magnetic field. If a piece of electrically conductive metal is close to the coil, eddy currents will be induced in the metal, and this produces an alternating magnetic field of its own. If a second coil is used to measure the magnetic field, the change in the magnetic field caused by a metallic object will be detected.