Beat poet Allan Ginsberg's "Howl" is unquestionably a poetic celebration of the counterculture of the 1950s (he first shared it at a poetry reading in 1955). While it is a poem, "Howl" breaks many of the traditional conventions of poetry--which should not be a surprise in a poem that celebrates the unconventional.
Conventions in any form of literature are those elements which define that particular form; in poetry, the conventions include such elements as rhyme, meter, stanza, and the use of figurative language, imagery, and symbolism. This poem is replete with examples of the last two items on the list; in fact, much of the imagery is graphic and does not just appeal to the senses but at times seem to scream at them. For instance:
who bit detectives in the neck and shrieked with delight in policecars for committing no crime but their own wild cooking pederasty and intoxication...
He also uses symbols to represent the culture he and what he calls "the best minds of my generation" are rebelling against: money, authority, capitalism, churches, metropolitan cities, schools, and more.
One of the poetic conventions Ginsberg does not follow is rhyme. There is no evidence of rhyming in any of the three stanzas, and that is certainly a deliberate choice on his part. Rhyming is restrictive and requires thoughts to be expressed within a general pattern; most of the time, a pattern of rhyming also requires a kind of consistency between stanzas. Of course poets are free to make purposeful shifts in a rhyming pattern, but even the digression is part of a larger rhyme scheme which adds to the meaning of the work. Particular rhyming patterns are connected to particular poetic forms, most of which have been in existence for hundreds of years, at least. For this now statement about a new thing, Ginsberg did not confine himself to something old and entrenched.
Meter is another poetic convention which Ginsberg flaunts in this poem. Meter is the regular pattern of stressed and unstressed syllables in a line of poetry, and it serves to give the poem a rhythmical reading--which in turn contributes to meaning. There is no evidence of a consistent meter anywhere in this poem, except perhaps for the "I’m with you in Rockland" line in the third stanza. Instead, Ginsberg has written his poem in a passionate kind of rhythm that rises and falls, waxes and wanes, as his emotions lead him. This is why it still sounds like a poem to us, despite the fact that there is no metrical pattern.
Ginsberg also takes the convention of stanzas and punctuation and revolutionizes them. Instead of stanzas in equal parts and relatively similar forms and containing more traditional forms of punctuation, he gives us three wildly different stanzas and quite unconventional punctuation. The first stanza (part) is one long run-on sentence made up of example after example of those "best minds" who have been "destroyed by madness." The second stanza is entirely different from the first (or the third) and, after the initial question, every line or exclamation ends with an exclamation point. The effect, of course, is that readers feel as if they are being shouted at with some intensity. The final stanza is a kind of chant. After the initial exclamation point, there is no punctuation, including no period at the end, an obvious statement that his commentary against the culture does not end with this poem.
Ginsberg's message is countercultural and the form he uses is equally nontraditional.