An "elegy" is a poem about a dead person. These types of poems can be sad and mopey or grand and celebratory. "The Unknown Citizen" is of the grand and celebratory variety, but it’s also a satire, which means that it is making fun of the person it pretends to celebrate. There’s not much that’s grand about the Unknown Citizen. We know that he’s dead because the speaker refers to him in the past tense, and also because the monument for "The Unknown Citizen" reminds us of "The Tomb of the Unknown Soldier," which was created to honor soldiers who died in battle but whose remains were never identified.
The speaker of the poem thinks he is paying a lot of nice comments, but most of his compliments amount to saying that the UC never caused anyone any problems. He sounds like the guy who agrees with everything and whom everyone calls "a nice person." This is called "damning with faint praise," because the praise is so weak and half-hearted that we know it’s just masking his utter insignificance. And, just so you know, Auden didn’t write satiric elegies exclusively; he also wrote two of the best heartfelt elegies of the 20th century: "In Memory of Sigmund Freud" and "In Memory of WB Yeats."
At a time when many poets were throwing themselves fully into unrhymed free verse, Auden was happily continuing the tradition of writing in rhyme. His rhymes don’t sound old-fashioned, either, although sometimes they seem ironic. When people complain that his poetry doesn’t rhyme anymore, you can point them back to Auden’s work.
However, he was far from a conventional poet, and "The Unknown Citizen" doesn’t follow a standard rhyme scheme. Instead, it alternates between a few different, simple rhyme schemes. The simplicity of Auden’s rhymes is striking, as if he had nothing to prove. Which he didn’t, considering that he was also a whiz with more complicated forms of rhyme.
The poem begins with an ABAB pattern, but then switches to a rhyming couple (AA, BB, etc.), after which he starts hopping around a lot. Some of the rhymes are sandwiched between other rhymes. Check out lines 8-13, which follow the pattern ABBCCA. You think he’s not going to rhyme anything with "Inc.", but then, five lines later, he comes at you with "drink." These two words are so far away that you might not even realize he was rhyming, but we bet your inner ear did.
Finally, the rhythm of the poem roughly centers on the anapest, a metrical foot that has two unstressed beats followed by a stressed beat. In the future, whenever you hear the tricky-sounding term anapest, think of the first two lines of "’Twas the Night Before Christmas," which has eight perfect anapests in a row: "’Twas the NIGHT before CHRISTmas and ALL through the HOUSE, / not a CREAture was STIRing not EVen a MOUSE." Auden doesn’t ever use that many anapests in a row, but they are pretty common in the poem, such as at the beginning, "He was FOUND by the BUReau . . ."
Now, if this meter sounds corny to you, then you’re on to something. Remember that this is a dramatic poem, and the fictional speaker is a government bureaucrat, so we would expect it to sound a bit corny, like something you might read on a greeting card…or a monument.