Sentence examples for a rat from inspiring English sources

The phrase "a rat" is correct and usable in written English.
It can be used in various contexts, such as referring to the animal, or metaphorically to describe someone who betrays others or informs on them.
Example: "He felt betrayed when he discovered that his friend was a rat, leaking information to their rivals."
Alternatives: "a snitch" or "a traitor".