Metal detectors are devices used for detecting metallic objects from the soil, people, or cargo. Metallic objects can be treasures buried underground, discarded pieces of aluminum, jewelry or valuable coins. Metal detectors satisfy all needs in humanitarian, industrial and security fields. Knowledge on how metal detectors work helps people to use metal detectors more effectively.

A typical metal detector comprises four main parts such as stabilizer, control box, shaft, and search coil. The search coil is also called search head, loop or antenna. The stabilizer provides excellent stability for metal detectors in use. It is placed near the hand grip area. The control box is the brain of a metal detector. It consists of a microprocessor, circuitry, speaker, controls and batteries. A shaft is used to connect the control box and search coil. It is adjustable and can be set at a level according to the height of the user. The search coil senses the presence of metal components.

Metal detectors work in a very simple manner, based on the principle of electromagnetism and its effects on conductive metals. The transmitter, located inside the metal detector's search coil, makes use of battery power to generate a penetrating electromagnetic field. When it enters the ground, the metal objects below the ground become charged with magnetism. The magnetized metallic objects under the ground send a signal to the control box. The speaker in the system control pack or control box amplifies the signal and the user hears the beep sound. Some modern metal detectors display the type of metal found below the ground. They also inform how deep the metallic objects are located.

The various technologies used in metal detectors are very low frequency (VLF), Pulse Induction (PI) and Beat-frequency oscillation (BFO). Metal detectors utilize one of these technologies. VLF technology, also called induction balance, is perhaps the most popular detector technology nowadays. It is highly successful in detecting anything metallic and uses two coils, a transmitter coil and a receiver coil. In this case, a sine wave is transmitted with one coil and received with the other. Compared to VLF technology, pulse induction and beat-frequency oscillation are more complicated. They can be operated in detecting very small objects.