Other sites on the internet have covered this topic in great detail, so much so that the explanations seems to be more on the science of transceiver devices, transmissions, as well as electro-magnetic fields, eddy currents, electromagnetic field distortion, and so on and so on and so on. All very scientific and boring to read, and in many cases difficult to understand....Not so the following simple explanation....

How Metal Detector's Work

You don't need to understand all the science of how a metal detector finds various metals. You can find coins, rings, jewelry, gold, relics, artifacts, small buried caches and even deep treasures without knowing scientifically how a metal detector works. Look at this simple illustration....,

Illustration 'A' shows a typical metal detector user. He has followed the instructions supplied by the manufacturer and has his metal detector turned on. After testing his detector on some surface targets (coins) to make sure it is working, he now starts searching for buried coins and treasures.

Notice the "red" signal pattern being transmitted from the searchcoil into the ground. (Note: we have enlarged the illustration of the signal pattern for easier understanding). As long as the signal entering the ground does NOT come in contact with metal, there will be no audio signal, no flashing light, no vibration, nothing will happen.

Illustration 'B' shows what happens when the detector user's metal detector search pattern comes in contact with metal objects, in this case both shallow and deep coins. When the search pattern touches metal it interrupts the transmitted signal and this interruption or disturbance of the search pattern will cause the metal detector to alert the detector user (you) with an audio signal, usually a distinct loud sound. In some cases flashing or blinking lights will accompany the audio signal.

Simple isn't it?