This topic brings to mind the students who have told me, "Homer's The Odyssey sure doesn't sound like poetry to me!" Likewise, whenever I make reference to poetic elements in Genesis 1, some Young Earth Creationist will always reply, "Genesis 1 is nothing like the poetry we see in the Psalms." Even if we leave that claim unchallenged, it is much like saying that Beowulf can't be poetry because it doesn't sound like "Mary had a little lamb. It's fleece was white as snow. And everywhere that Mary went, the lamb was sure to go."
Of course, most of the people who reprimand me by saying that Genesis 1 isn't poetry (1) can't read Hebrew poetry, and (2) can't define what constitutes poetry. Indeed, defining poetry is no easy task! I would encourage readers to Google the topic and try to draft a one sentence definition of poetry. Better yet, try to compose a single paragraph which provides exhaustive heuristic rules for determining what is and isn't poetry for any given text from every culture, language, and era of human history.
With those complexities in mind, consider that Genesis 1--and/or the oral tradition on which it is based---may be the product of a language and culture which predates Moses by many centuries. It may be a relic of an ancient literary structure complete unknown to us---just as it may be impossible to determine if any given phrase from an ancient text had an idiomatic meaning lost long ago.
The ancient Hebrews were intelligent people. They realized that days with evenings and mornings made no sense if no sun yet existed---unless the recurrent evenings-and-mornings chorus had another kind of purpose. They would have noticed multiple poetic elements in the Genesis creation pericope that a lot of English Bible readers in our day entirely miss. Yet, even the chiasms are evident to modern day English readers, if they are first explained and circled. Those are patterns which are poetic elements.
As I've often noted, if Genesis 1 had always been part of the Psalms and Seventh Day Adventist prophetess Ellen White hadn't suffered a brain injury as a child (which led to hallucinations which included visions of the ancient earth and her "flights" to other planets), I doubt that George McReady Price would have written a book which led John Whitcomb Jr. to interpret Genesis 1 far more literally and "scientifically" in ways which launched the Young Earth Creationist "creation science" set of hermeneutics we know today.