by Ellen Gwin

What is alliteration?
Alliteration is the repetition of consonants (and sometimes vowels) at the beginning of two or more consecutive words. 

What about consonance and assonance?
Consonance is the repetition of solely consonants throughout consecutive words. These words can go at the beginning or in the middle of a word. 
Assonance is the repetition of solely vowels throughout consecutive words. These words can go at the beginning or middle of a word. 

1.To set the mood
Different sounds are linked with different connotations; one can use this concept to their advantage in poetry.
For Example:
S’s bring about a mood that feels whispered and intimate (or a snake-like)
H’s to makes the poem sound soft, hushed, or breathy 
R’s sound “French” and romantic (or like pirates)
B’s & P’s seem to boom or pop out loudly

2. Because it sounds pleasant
The repetition of consonants (or in some cases, vowels) sounds pleasing to the ear. This is because it provides a sense of rhythm to the poem and indicates how it should be read. This provided rhythm allows the reader to feel more closely connected to the work.
For Example:
The bumbling bear bellowed behind a beehive.
Slither snakes spoke of sinister stories.
Fiddling foxes found refuge in Finland.

3. To grab readers’ attention
One can use alliteration to simply draw attention to a specific set of alliterative words or
One can use alliteration to draw attention to themes throughout your poem through the use of alliteration at key moments with similar ideas in mind.