The message of "To His Coy Mistress" is that life is short, time moves quickly, and thus that the speaker and his beloved should make love now. The speaker declares that if they had limitless time, he could woo her slowly, spending thousands of years complimenting her various admirable features. He makes clear that this would be the ideal state of affairs:
For, lady, you deserve this state,
Nor would I love at lower rate.
The problem, however, is time, whose swift passage prevents such luxurious courting. The speaker argues that his beloved's beauty will fade and that she will eventually die, at which point the opportunity for pleasure will be past and her "honour" will mean nothing.
Now, however, the speaker's mistress is young and beautiful, and so he argues that they should act "like amorous birds of prey"—that is, they should "devour" their time and make the most of it rather than allow it to simply run out. They cannot stop time or prevent it from passing so swiftly, but they can certainly, he argues, enjoy their time together to the fullest, which to him means making love. At the end of the poem, the speaker presents a humorous challenge to the sun:
Thus, though we cannot make our sun
Stand still, yet we will make him run.
Here, he acknowledges that time, represented by the sun's passage, cannot be defeated or altered. But he imagines that their amorous embrace might cause the sun to hasten its course.