Which part of a plug is responsible for connecting metal pieces in an appliance to safety?

The ground prong in a plug plays a critical safety role by connecting the electrical system of an appliance to the ground. This connection helps to prevent electric shock by providing a path for excess electrical current to flow safely into the ground in the event of a short circuit or equipment malfunction. When an appliance is properly grounded, if a fault occurs, the ground prong directs the potentially hazardous electricity away from the user and into the earth, significantly reducing the risk of electric shock.

In contrast, the first prong and second prong typically carry the live and neutral currents, respectively, which are necessary for the appliance's operation but do not provide a safety connection. The third prong, also known as the ground prong, is thus essential for ensuring that appliances operate safely, particularly in wet or high-risk environments.