In the wake of slam poetry and “spoken word,” confused audiences have asked themselves what poetry actually is. I think people tend to imagine that it looks and sounds like an English sonnet, with rhyming couplets and metered form (we all did once, right?). It might even have some kind of resolution: a neat bow of a message tying the whole poem together at the end. A poem might look this way, obviously, but I think we’ve moved on since Wordsworth. Poets like Walt Whitman (“Song of Myself”) pioneered free verse, or unrhymed, unmetered poetry, free of form or convention.
Poetry was able to say what it wanted, how it wanted. Postmodern writers came back to form from time to time, but usually to satirize their predecessors (think Annie Finch’s “Coy Mistress”, a response to Andrew Marvell’s “To His Coy Mistress”, or Billy Collins “Litany”).