What is an example of metaphor in the novel, We Are Okay?

“I [Marin] burrowed under like a rodent in a wall” (184).

Why does a rat burrow in a wall? Perhaps to hide from the things it fears in the world, which is exactly what Marin does in this instance. Marin ran from her problems in California, but she cannot hide from the thoughts with which her brain is now inundated.