A metal detector is, as the name suggests, an electronic device that detects metals. Now, the topic of “which substances are metal” is a broad spectrum in itself, so we won’t go there.

But it is very necessary to know what metals will set off a metal detector? Whether you are a novice who wants to learn about metal detecting or a traveler planning on going through the airport security smoothly.

So in this article, I will try to cover all about the metal detectors and the metals, of course, with a beaconing hope that readers will find it to be informative enough to hear the “bleep bleeps” where you want to hear and do not hear those where you don’t want to.

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Metal Detectors: How They Work?

It is crucial to at least have the basic knowledge about how a metal detector works when you plan to engage in metal detecting.

Well, the 101’s of a metal detector is that it contains a transmitting coil, a receiving coil, and obviously a medium to let the user know about detected metals, a speaker or an LED indicator.

How they find the metals? This question needs a little more science stuff in its answer. Therefore, I’ll take you to 1860’s Scotland, where the genius physicist James Maxwell discovered the connection between Electricity and Magnetism.

According to him, if there’s a changing electric field, there will be a changing magnetic field also as the consequence of the former. Metal detectors use this law to detect metals.

When a metal detector is on, its transmitting coil will create a magnetic field because of the electricity flowing through its wires.

This magnetic field will affect the electrons of the metals that are nearby. This disturbance in the electrons will create a second magnetic field around the metal which will be received by the receiving coil of the metal detector.

Then, it will set off the metal detector through a speaker or other indicators, simple as that.

What Metals will Set off a metal detector and what metals that Don’t

I’ve already stated that the electric conductivity of metal matters when it comes to detecting it by a metal detector. The periodic table gives us about 91 elements which are considered as metals.

But will all of them set off a metal detector equally? Generally, gold, silver, brass, copper, aluminum, etc are some metals with higher conductivity that are easily detectable by most of the metal detectors.

Metals that are non-ferrous or stainless steel are harder to find due to their lack of enough electric conductivity. So to detect them one needs more high power metal detector.

So when people ask what metals set off a metal detector? Or you can put it as what metals cannot be detected by a metal detector, the answer is simple. It solely depends, as I’ve said, on the conductivity of the metal or the sensitivity of the magnetic field created by the metal detector.

Metal Detectors at the Airport

Metal detectors are non-detachable part of the airport security system. But the concept and mechanism used here are much more complicated and advanced than your regular metal detectors.

People may wonder, what metals do airport metal detectors detect? The answer is almost every type and any type. But it is not that black and white. For example, does stainless steel set off airport metal detectors?

Absolutely. But it may choose to stay silent upon detecting gold. Both will depend on the amount and situation. Generally, airport securities ignore the small and normal amount of gold while detecting.

It is wise to inform the customs officers beforehand if you have any medical implantations in your body as these are often made of stainless steel. Will a SIM card or SD card set off a metal detector? It may or may not, depends on the metal detector.


Metal detectors have been a blessing for both the metal detecting enthusiasts and the security system. Though, metal detectors can cause us occasional embarrassment by going off unwantedly.

To avoid these learn how to stop a metal detector from going off by avoiding all the acts and objects that set it off to the minimum. It will save you and others in line a lot of time.

With time, technology has advanced and metal detecting has become more accurate and less time-consuming. Sometimes metal detectors bring us joy by discovering treasures and sometimes it keeps us from the harm by detecting weapons and harmful instruments.

So, despite the minor inconveniences, metal detectors are here to help.