In this poem, the speaker addresses Love and expresses his feelings about the way that Love is making both himself and his beloved suffer because of their feelings for one another. An extended metaphor that is used in this Sonnet is that of slavery, as the speaker describes suffering for love and being subject to its force as a kind of slavery:
Is't not enough to torture me alone,
But slave to slavery my sweet'st friend must be?
The speaker therfore wishes he could sacrifice himself in exchange for the liberty of his beloved, and, in declarative sentences, tries to strike a deal with Love to ensure his beloved's freedom:
Prison my heart in thy steel bosom's ward,
But then my friend's heart let my poor heart bail...
The speaker's love for his beloved is so strong that he would glady sacrifice himself if it would spare his beloved from the kind of slavery that love gives. Finally, however, the sonnet ends with a recognition of the power of love and how the speaker belongs to Love and is totally dominated by it:
...for I, being pent in thee,
Perforce am thine, and all that is in me.
The poem then is an expression of the power of love and the way that it can reduce us to a form of slavery as we languish under its impact.