In "To His Coy Mistress," the impatient speaker is trying to persuade his beloved to make love to him. He wants her to make up her mind in a timely fashion.
Therefore, the speaker says that while he adores his beloved and would gladly spend 30,000 years praising all her body parts, such as one hundred years on her eyes and two hundred on each breast, they don't have time for that. They are not going to live forever. Time's "winged chariot" is bearing down on them as he speaks, ready to flatten them at any moment.
He notes that once she is a dead, she will be in a crypt, accompanied by worms. At that point, she will not be able to enjoy any sensual pleasures. She needs to indulge in what life has to offer now, before it is too late.
Finally, the speaker paints a picture of what they should do to defeat time, which is portrayed as their enemy. They should grab hold of the present moment greedily and get all the pleasure possible from it:
Now let us sport us while we may,
And now, like amorous birds of prey,
Rather at once our time devour
This expresses the "carpe diem" or "seize the day" theme that was popular in the seventeenth century. The speaker is arguing that if his beloved doesn't enjoy what she can now, she may lose the possibility to do so.