How do poetic devices (alliteration, cacophony, euphony, metaphors, onomatopoeia, personification, rhyme, symbols, etc) enhance a poem?
Each different device enhances the poem in a different way but they are all in place to help the reader imagine the scenario and to feel emotions.
Alliteration is used to emphasise a certain section of the piece. If a certain phrase has particular significance then the author would use alliteration to draw your attention to it.
I don't know what cacophany or euphony are.
Metaphor is there to provide clarity for the reader by giving an expample through imargery.
Personification is another form of metaphor.