A metal push button switch is a momentary or non-latching switch maintain or lock which causes a temporary change in the state of an electrical circuit only while the metal switch is physically actuated. An automatic mechanism (i.e. a spring) returns the metal push switch to its default position immediately afterwards, restoring the initial circuit condition. There are two types:
1.A push to make switch allows electricity to flow between its two contacts when held in. When the button is released, the circuit is broken. This type of metal switch is also known as a Normally Open (NO) push button Switch. (Examples: doorbell, computer case power switch, calculator buttons, individual keys on a keyboard)
Push-to-make switch electronic symbol
2.A push to break switch does the opposite, i.e. when the button is not pressed, electricity can flow, but when it is pressed the circuit is broken. This type of switch is also known as a Normally Closed (NC) metal button Switch. (Examples: Fridge Light Switch, Alarm Switches in Fail-Safe circuits)
Many metal Push switches are designed to function as both push to make and push to break switches. For these push button switches, the wiring of the switch determines whether the switch functions as a push to make or as a push to break switch.