The simplest switch has two pieces of metal called "contacts". When the two contacts are in contact, the current forms a loop, and when the two contacts are not in contact, the current is open. When choosing a contact metal, consider the degree of corrosion resistance, because most metals will form an insulating oxide after oxidation, making the joints unable to work properly. The choice of contact metal also needs to consider its conductivity, hardness, mechanical strength, cost and whether it is toxic.
Corrosion-resistant metals are sometimes plated on the contacts. It is usually plated on the contact surface of the contacts to avoid the effects of oxides. Sometimes the contact surface also uses non-metallic conductive materials, such as conductive plastic.
In addition to the contacts, the switch also has a movable member to make the contact conductive or non-conductive. The switch can be divided into a toggle switch, a push button switch, a rocker switch, etc. depending on the movable member. The movable member can also be other types of mechanical linkages.