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. Philip Hobsbaum identifies three major types of free verse:

Free iambic verse, which is an extension of the work of the Jacobean dramatists. Practitioners of this sort of free verse include: T. S. Eliot, Hart Crane, and W. H. Auden.
Cadenced verse in the manner of Walt Whitman.
Free verse proper, where the discrepancies and variations of meter are centre stage.

Cadenced verse is today based on rhythmical phrases that are more irregular than those of traditional poetic meter. When it is used, it tends to follow a looser pattern than would be expected in formal verse. Free verse does away with the structuring devices of regular meter and rhyme schemes; other traditional elements of expression, such as diction and syntax may still be prominent.

The poetry of Walt Whitman provides many illustrations of Free Verse including his poem “Song of Myself”.

Song of Myself
by
Walt Whitman

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.

This particular poem is quite long if you are interested you can read the full version HERE

Some poets think free verse to be too limiting. In 1922 Robert Bridges voiced his reservations in the essay ‘Humdrum and Harum-Scarum.’ Robert Frost, later remarked that writing free verse was like “playing tennis without a net”.

As the name vers libre suggests, this technique of using more irregular cadences is often said to derive from the practices of 19th century French poets like Gustave Kahn. However, in English it can be traced back at least as far as the King James Bible. Walt Whitman, who based his verse approach on the Bible, was the major precursor for modern poets writing free verse, though they were reluctant to acknowledge his influence.