Poetry’s ability to establish patterns on multiple levels (sounds, meters, rhyme schemes) means that formal and prosodic evidence is best talked about in terms of its interaction with the content of the words that they condition. In other words, it’s good to note that two words rhyme; it’s better to note that their rhyming creates a productive pairing (you should always consider rhyming words a set to analyze, for example, since your attention has been drawn to them, usually also by the rhythm of the lines). It’s good to be aware that the poem is setting up metrical patterns within its lines; it’s better to realize that those patterns are altering the way you receive (they are mediating) that information. And so on.
But consider, too, that the fact that poems can change up the ways that they have been mediating their lines throughout the text means that they not only can change their message (and messenger), but that the visual form of the poem contains dynamic, rather than static, information. Some poems are short, exist in one stanza (the Italian word for “room”) have only one rhyme scheme, and never deviate from their metrical pattern. But most poems mix it up.
Another thought: if you set up a pattern, you can also use that as a useful container to convey data. And if you are using a familiar (prefab) pattern, you can draw on generic conventions to heighten your reader’s ability to expect certain things from your patterns. For example, I’ve talked previously about the eighteenth-century’s vogue for the heroic couplet, which is a long string of perfectly rhymed couplets in iambic pentameter. Pope’s “Epistle to Arbuthnot” is a great example of how poets can use the heroic couplet as a sense unit, by which we mean that the reader begins to expect an entire thought to be constructed, executed, and finished within that couplet (there’s nearly always a full stop after the second rhymed word). So, when we read a poem like Browning’s “My Last Duchess,” which is also in heroic couplets, but which is enjambed over almost every line, the experience is jarring. As happens often when I teach the poem, I have to remind students to pay attention to the rhyme scheme at all, since it seems to be speech which overflows its bounds. But that deviation from the normal heroic couplet mode certainly speaks to the Duke’s hubris. More conventionally, the Italian (sometimes called “Petrarchan”) sonnet usually has an octet of eight lines and a sestet of six lines which have different rhyme schemes. This format has been used so often that it’s reasonable to assume that the first eight lines of a sonnet convey a single thought or emotion, and that there is a distinction then to be made between the first eight lines and the last six lines. We even came up with a term for this turn, the volta. So we never want to leave our analysis in two pieces – one about the content, and one about the form. We always, always want to bring form and content into conversation with each other when we read poems.