Goal metrics are explicit measurements used to inform, and keep track of, a players performance or progress in a game. They are also used to determine whether a goal has been reached or not.
Goal metrics also help players keep track of their performance across multiple game sessions. Thus, players can keep track of their scores and determine which particular session was the best on the basis of the highest score received. It can also serve a powerful social function by providing different players with a way to compare their performance.