Metal detectors have been in existence for many years. In their former years, they were develope as a way to detect explosives. However, the first Metal Detector was invented by Alexander Graham bell in1881. Since then, the concept of how they work has remained largely unchanged. They work on the two concepts of electricity and magnetism. Refinement of this technology over the years has led to the development of the different types of metal detector currently in existence. There are some types of metal detector: VLF detector, pulse induction and beat frequency oscillation.