The simplest switch has two pieces of metal called "contacts" that make the current loop when the two contacts touch and open the current when the two contacts do not touch. The use of contact metal should consider the degree of corrosion resistance, because most of the metal oxide will form an insulating oxide, so that the contact does not work. Selection of contact metal also need to consider its conductivity, hardness, mechanical strength, cost and whether toxic and other factors.
Corrosion-resistant metals are sometimes electroplated on the contacts. Generally plated contacts in the contact surface, in order to avoid the oxide and affect its performance. Sometimes the contact surface will also use non-metallic conductive materials, such as conductive plastic.
In addition to the contacts in the switch, there will be a movable member to make the contact open or non-conductive, the switch can be divided into different parts according to the movable lever switch (Toggle switch), push switch, Rocker switch , While the movable member can be other types of mechanical links.