Figurative language refers to any figure of speech used to make language more effective. Figurative language is essentially created when a writer uses language in a non-literal way to create more descriptive meaning. There are many different forms of figurative language, and some of those include metaphor, simile, personification, oxymoron, hyperbole, symbolism, etc. We can definitely see a couple of instances of figurative language in the American band Fun's song "We are Young"; some of the figurative language include personification and metaphor.
Personification happens when a writer attributes human characteristics to inanimate objects. Dr. Wheeler gives us the example, "The ground thirsts for rain; the wind whispered secrets to us" ("Tropes"). We can find personification in the first stanza in the song in which the speaker describes his lover "waiting for [him] across the bar," but his seat has been "taken by some sunglasses." Literally, this phrase is saying that his seat has been occupied by a pair of sunglasses, but that's not literally what happened since that's an impossibility. Instead, the speaker is using the term sunglasses to describe a man wearing sunglasses. But, in just referring to sunglasses taking the seat, he is personifying sunglasses.
A metaphor is created when we compare two unrelated objects by saying something is something else. The comparison helps create more descriptive meaning. Dr. Wheeler gives us the very classic example from pop-culture, "This is your brain on drugs" ("Tropes"). A metaphor can be found in the song's fifth stanza:
We are young
So let's set the world on fire
Here, the speaker is not suggesting that the whole world literally be set on fire. Instead, he is using the term fire to speak of emotions, like passion, by describing emotions as fire. The speaker is also using the term world in a relative sense. He is not speaking of the literal whole world; instead, he is speaking of his own personal world, limited by his own personal experiences. Therefore, by saying "let's set the world on fire," he is essentially metaphorically saying, "let's experience passion in our own private world."