The poem "Ode to Autumn" by John Keats is a masterpiece. The structure is beautifully crafted. Here are some points to bear in mind.
First, there are three stanzas.
Second, the meter is iambic pentameter. This is a commonly used meter in English poetry. The rhythm of the meter is based on iambs, which means the meter is unstressed followed by a stressed syllable. There are five iambs (hence, pentameter).
Third, there is also a rhyming scheme. Here is the pattern: ABABCDEDCCE.
There is also a temporal structure to the poem, which shows the progression of a day. The first stanza deals with morning. The second stanza is afternoon, and in the final stanza, it is night. We can also say that there is also a progression of seasons - spring, summer, and fall.