The structure of a poem can reveal a great deal about a poem, especially if the word “structure” is defined in fairly broad terms. Among the things that a poem’s structure may reveal about the work are the following:

• The poem’s genre.  For example, a poem with fourteen lines and certain standard rhyme schemes will tend to be a sonnet. Limericks also have rigidly definited structures, as do haikus and many other different genres of poems.  In the case of limericks, we can expect that the shape of the poem will tell us something about its tone; limericks are almost always comical poems.
• The intent of the poem.  Poems with highly elaborate structures – such as sestinas – are almost always written as much to display the skill and cleverness of the poet as to comment on any particular theme.  We are usually less impressed by the message of a sestina than we are by the sheer artistic talent of the poet in pulling off such a difficult task. Poets write sestinas partly to be admired (if they are successful) for their poetic skill.
• The era during which the poem was written.  For example, so-called “hieroglyphic poems” (such as George Herbert’s “The Altar” or “Easter Wings”) tended to be produced in the seventeenth century but then went out of fashion, as least until fairly recently. The structure of a poem, in this sense, may suggest the historical period that helped originally give the poem part of its purpose and meaning. Poems with heroic couplets and with highly end-stopped lines tend to be more characteristic of the eighteenth century than of the twentieth. Rejections of certain kinds of structures, and especially rejection of the notion of conventional, prescribed, traditional structures, tends to be to tell us a lot about the values embodied in particular kinds of poems.  It takes only a glance at some of Ezra Pound’s “Cantos,” for instance, to see that Pound is emphatically revolting against the kind of poetry that had been typical, say, of the nineteenth century.  Similarly, one has only to read one of Philip Larkin’s poems after reading some of Pound’s Cantos to see that Larkin has turned away from the kind of structures Pound favored. Similarly, the long-flowing lines of Walt Whitman differ strikingly from the neat, brief poems of Emily Dickinson, and these differences imply a good deal about the temperaments, purposes, and values of the two poets. Thus, this:

Beat! beat! drums! -- blow! bugles! blow!

Over the traffic of cities -- over the rumble of wheels in the streets;

Are beds prepared for sleepers at night in the houses? no sleepers must sleep in those beds,

No bargainers' bargains by day -- no brokers or speculators -- would they continue?

differs from this:

Come slowly, Eden!

Lips unused to thee,

Bashful, sip thy jasmines,

As the fainting bee,

Reaching late his flower,

Round her chamber hums,

Counts his nectars--enters,

And is lost in balms!

And the difference is not simply one of word choice or meaning, but emphatically one of structure as well.