What are the thematic structures in Andrew Marvell's "To His Coy Mistress"?

This poem is structured like a rhetorical argument. The poem can
be divided into three sections : if (I had all the time in the
world); but (we don't); therefore(we
should act). The poem is an elaborate and eloquent argument to having
sex.

In the first section of the poem, the "if" section, the speaker
tells his coy mistress that if they had all the time in the world they would first explore the
world separately, and that once they met he would spend many, many years to adore each of her
body parts. Nothing would be rushed; there would be no need for
haste.

In the "but" section of the poem, the speaker brings their
situation back to reality. In reality he hears "time's winged chariot hurrying near." Time is
always moving forward and we are all on our way to the vast eternity of death. In this section he
rather explicitly tells the young lady that once she dies and is in the "marble vault . . . then
worms shall try that long preserved virginity." He is suggesting that she might as well lose her
virginity to him in her lifetime when she can enjoy it, otherwise the worms will get it
eventually. He is trying to creep her out! He ends this part of the argument by reminding her
that the "grave's a fine and private place, but none, I think, do there embrace." The grave may
be private, but is not a fun, warm, or loving place.

The final
aspect of the argument is that they should embrace carpe diem -- seize the day-- and enjoy their
sexuality. He uses several images that suggest youth and passion. He comments on the "morning
dew" which uses the day of life metaphor to reference her youth. He mentions "instant fires"
which is a stock metaphor for passion. He draws the image of "amorous birds of prey" which
suggests physical energy and passion. He uses the image of them rolling their "sweetness up into
one ball" which suggest sexual joining, while "tear our pleasures with rough strife thorough the
iron gates of life" is likely a reference to the hymen being broken upon intercourse. The
language is vivid and strongly sexual because he is making the final point of his argument. First
he flatters her, then he points out reality, and he ends it with language that entices her to
believe his argument.