Free Verse is a form of Poetry composed of either rhymed or unrhymed lines that have no set fixed metrical pattern. The early 20th-century poets were the first to write what they called "free verse" which allowed them to break from the formula and rigidity of traditional poetry. The poetry of Walt Whitman provides many illustrations of Free Verse including his poem "Song of Myself".
Song of Myself
I celebrate myself, and sing myself,
And what I assume you shall assume,
For every atom belonging to me as good belongs to you.
I loaf and invite my soul,
I lean and loaf at my ease observing a spear of summer grass.