In a poem describing the saintly awesomeness of love, you better believe you're going to get some sound effects. Donne uses a whole grab-bag of techniques in this poem in order to emphasize the harmony that our speaker is experiencing in his relationship.
We can start with alliteration, which grabs us by the earlobe in the very first stanza. Just check out the repeated L words in line 1: "For God's sake hold your tongue, and let me love" and the F words (not those F words) in line 3: "My five grey hairs, or ruin'd fortune flout." But Donne is just getting started, folks.
For example, he busts out some major consonance going forward in the poem. In particular, he seems to have fallen in love with L sounds. We have L's in lines 16-17: "Soldiers find wars, and lawyers find out still/ Litigious men, which quarrels move." And we get a bunch more in the following passage:
Our legend be, it will be fit for verse;
And if no piece of chronicle we prove,
We'll build in sonnets pretty rooms;
As well a well-wrought urn becomes. (30-34)
In fact, there are L sounds scattered throughout the poem, which seems appropriate to a lover who is loudly loving how lovely love is.
And still the sonic hits keep coming. We have assonance with the long I echoing in "We die and rise the same, and prove" (26) and even internal rhyme in lines 28-29: "We can die by it, if not live by love,/ And if unfit for tomb or hearse." Okay, so "it" and "unfit" aren't the most dynamic rhymes, but they still give us a harmonious echo that fits our speaker's praise of love.
Finally—as if that wasn't enough—we get lots of anaphora in this poem. The repetition of "your [blank]" ties line 4 together: "With wealth your state, your mind with arts improve," as the repetition of "Call [blank]" does with lines 19 and 20: "Call's what you will, we are made such by love;/ Call her one, me another fly." And did you notice that each stanza's first line and each stanza's last line ends on the same word? That's right, in a poem filled with sonic harmonies, Donne was smart enough to make sure that the last word in the poem was "love."