A metal detector is an electronic instrument which detects the presence of metal nearby. Metal detectors are useful for finding metal inclusions hidden within objects, or metal objects buried underground. They often consist of a handheld unit with a sensor probe which can be swept over the ground or other objects.
Metal detectors are used for airport and building security to deter- mine whether guns, knives, or other weapons are being transported onto aircraft or into public buildings. The technology and efficiency of a security metal detector is much more advanced than that of an amateur treasure-hunting detector. There are two types of security metal detectors: the walk-through detector, and the wand detector.