"To His Coy Mistress" takes the form of a dramatic monologue, which pretty much means what it sounds like. The speaker of the poem does all the talking, which makes this a monologue, a speech by a single character. But, because he isn’t just talking to himself, but to another fictional character, the mistress, it’s "dramatic" – hence the term "dramatic monologue." Although the reader might identify with the speaker in a dramatic monologue, or even with the silent character addressed, there is always the sense that the reader eavesdrops on an intimate conversation. This sense is heightened in "To His Coy Mistress," because the speaker doesn’t give us any personal or biographical information about himself or the mistress to create separation between the characters and the readers.
The poem’s meter is "iambic tetrameter." Don’t let the fancy name scare you away. It’s not complicated. Even Dr. Seuss uses it, as in these lines from Green Eggs and Ham:
I would not like them here or there. I would not like them anywhere. I do not like green eggs and ham. I do not like them Sam I Am.
You can think of an "iamb" as a unit of poetry consisting of two syllables. This unit is also called a "foot." In iambic tetrameter each line has four (tetra) such feet, or eight syllables in total. Pick a line from your poem to test it. If you read the poem aloud, or listen to it in your head (in a normal speaking voice, of course) you will see that in each foot, or iamb, or pair of syllables, one syllable is stressed, while the other is not. Notice also that the poem has forty-six lines, or twenty-three pairs of lines. We call these pairs "couplets," and, in the case of "To His Coy Mistress," the two lines that make up each couplet rhyme with each other.