[HarryT]

Certainly there are "rules" for poetry, but you can choose to ignore them if you wish. But the skill in writing poetry is to make it fit a particular meter.

Eg, consider this fragment of Shakespeare (from "A Midsummer Night's Dream"):

Hippolyta, I wooed thee with my sword,
And won thy love, doing thee injuries.
But I will wed thee in another key,
With pomp, with triumph, and with revelling.

This may not at first glance look like poetry, but it is. It's "blank verse". Each line is in unrhymed "iambic pentameter", with 10 syllables and a stress pattern of "da DUM da DUM da DUM da DUM da DUM". Blank verse comes close to the natural speaking rhythms of English but raises it above the ordinary without sounding artificial. Shakespeare was the master of blank verse.

Have a go at writing blank verse. It's challenging and fun.