Here's why:
* Literal meaning: Literally, serving something means to provide food or drink to someone.
* Figurative meaning: In the phrase "justice is served," it means that someone who has done wrong is punished or held accountable for their actions. The act of serving is a metaphor for the process of delivering punishment or consequences.
Therefore, "justice is served" is a metaphor because it uses the literal act of serving to represent the abstract concept of punishment or fairness.