Recurring themes are found throughout Donne's work.
The younger Donne tended to pose as something of a rake, writing witty poems of satire and seduction. He belongs to the group of poets often referred to as Wits. These poems are slightly misogynistic and cynical, as in "Song" ("Go and catch a falling star"). Similarly, the dramatic monologue "The Flea" is a poem of seduction that uses wit as an animating force. Delighting in the verbal and mental dexterity the speaker of the poem displays, the woman, like the reader, becomes bewitched or seduced by the speaker, with the very preposterous nature of the persuasive tools more appealing that the plausible argument.
A second group of poems include highly romantic love poems, especially the aubades "The Sun Rising" and "The Good Morrow." Wit and audacity are displayed here as well, as the speaker picks an argument with the sun. But romantic love is more seriously explored in poems such as "Valediction: Forbidding Mourning," "The Canonization," and "Air and Angels."
In a later phase of Holy Sonnets (e.g., "Death be not proud" and "I am a little world made cunningly"), Donne contemplates mortality and the terror of being unloved or rejected by God and thus subject to death and damnation.
A common thread in each of these stages concerns the ability of the poet to use the force of personality and language to change reality. Even if the world can't be literally altered (the sun will still rise, death will still come), the mind can change one's orientation toward these realities through the power of imagination. A metaphysical poet, Donne is among the best in using far-fetched metaphors to poke at concepts and redefine them in ways that change how they seem to those willing to use their imagination is similar ways.
It's not surprising, perhaps, that another theme running through the poems is the self-conscious dramatization of creating poetry itself. In "Valediction," for instance, the speaker illustrates the difficulty of finding the exact metaphor to ease his beloved's grief at their separation. Stanza after stanza offers a comparison of what their love might be like (dying men, earthquakes, planetary motion, refined gold) until finally resting on the image of the twinned compass. Similarly, in "Batter my heart," the speaker seeks to develop an understanding of the nature of the soul in relation to God, moving from the conceit of a damaged pot to a besieged town to, finally, imprisonment. Resting on the most implausible of comparisons, the speaker uses the improbable to access a metaphysical truth not seen through ordinary means.