The Flea is the title and the central metaphor of the poem.

Another rhetorical question here that implies an irrational concern

Rhetorical Question - implying that her concerns are irrational.

Donne uses a lot of religious imagery throughout as well, this is one of a few instances.

The flea being able to "enjoy" something is a use of personification from Donne. Donne writes as though the flea can have a human like emotion in this case.

Hyperbole here as Donne exaggerates the significance of the flea, emphasizing the point that their sexual union would be a great loss or sin

Subtle pun - Donne refers to the woman's rejection as a form of self-murder, suggesting that by denying him, she is harming herself.

symbolism for sex

another example of symbolism for sex