How do the methods employed by Sylvia Plath in her poems enable her to explore their extreme subject matter?

Plath employs a variety of methods in her poetry which are sucessful in both creating tension and heightening the physical and mental pain which she describes.

In her poem "Daddy", the repetitive "d" sound echoes throughout the poem, thus creating an accusing tone throughout. ("You do not do, you do not do"). The harsh "d" sound created upon reading the poem aloud is further effective in becoming reminiscent of a child's nursery rhyme with the same repetitive sounds. Thus, whilst we read the poem, we are constantly reminded of Plath's young age when her father left her which creates empathy for the poet, as well as a sense of vulnerability. 

As well as use of sound, Plath uses language to explore the extreme subject matter she depicts in the poem. She refers to her father as a "vampire" who "drank my blood", thus the use of such metaphors enable the reader to understand her feelings of hatred towards her father.