a gate like structure that looks for hidden metal objects that could be used as weapons, like guns, knives or sharp objects Every package goes through an x-ray machine

an electronic device made of a large coil of

a portable electronic device which penetrates the ground magnetically in order to find traces of metal

an electronic device used for finding metal.

Metal detectors use electromagnetic induction to detect metal. Uses include demining (the detection of land mines), the detection of weapons such as knives and guns, especially at airports, geophysical prospecting, archaeology and 'treasure hunting'. Metal detectors are also used to detect foreign bodies in food, and in the construction industry to detect steel reinforcing bars in concrete and pipes and wires buried in walls and floors.