Why do ATM buttons use metal?

ATM machines in banks are generally metal numeric keyboards, which have the advantage of preventing leakage of secrets.

Think about it: when you press the password with your finger, the temperature of the keyboard will be changed. If we take photos with a thermal camera just after the transaction is successful, we can get the password by looking at the photos.
The advantages of metal keyboard are high metal conductivity and fast temperature change. Even if someone takes a picture with a thermal camera, it is difficult to observe the color and judge the order.

Have you ever thought about what the small cylindrical objects on the power cord, mouse, keyboard, laptop, printer and other devices are used for, and what is the meaning of their existence?

Yes, this small object was installed on purpose. These "small bumps" are called ferrite beads or ferrite chokes. Their only purpose is to reduce electromagnetic interference and RF interference.

Metal numeric keypad

In short, it is used to reduce unnecessary signal or noise.

We all know that when two electromagnetic devices are connected by cable, the cable acts as an antenna. So the problem is, like all antennas, these cables can also receive and transmit signals from other unrelated devices. The result is noise or interference of useless signals.

This is the necessity of the existence of ferrite beads, which can eliminate broadcast signals and ensure that the cable will not send any other interference signals than planned.

If you open these small lumps, you will find that there is a small cylindrical solid made of ferrite, which itself is magnetic.

Ferrite is made of iron oxide (i.e. rust) combined with other metals. It is black, hard and fragile. But its magnetism can effectively eliminate interference.