What is the effect of rhyme, rhythm, and metaphor in "A Poison Tree"?

“A Poison Tree” by William Blake appears in Blake’s collection The Songs of Innocence and Experience, in the collection's latter half (the “experience” poems). Throughout the collection, Blake writes a number of poems on shared topics that explore the nature of the world through innocent/naive and experienced/cynical eyes.

Rhythm:

An audible pattern in verse established by the intervals between stressed syllables.

In this poem, the rhythm is largely trochaic. A trochee is a pattern of a stressed or long syllable followed by an unstressed or short syllable. A trochaic pattern can be observed in the pronunciation of the word “Monday.” With a few exceptions, trochees are the dominant pattern throughout the rhythm of the poem. Notably, each line ends with a single stressed syllable, omitting the expected following unstressed syllable. This creates a jarring pause at the end of every line. Trochees also begin almost every line, and this pattern of starting and ending with a stressed syllable gives each line a sudden introduction and an abrupt ending.

Rhyme:

The repetition of syllables, typically at the end of a verse line…conventionally [sharing] all sounds following the word’s last stressed syllable.

The poem’s rhyme scheme is very simplistic, following a repeated AABB pattern for each stanza (the first two lines of each stanza rhyme, and the last two lines rhyme). This helps to create a natural boundary around each stanza. Though Blake was capable of writing complex verse, he often masks difficult concepts in simple aesthetic patterns.

Metaphor:

A comparison that is made directly…or less directly…but in any case without pointing out a similarity by using words such as “like,” “as,” or “than.”

The extended metaphor of “A Poison Tree” is one of the harmful “fruits” of wrath and anger that is allowed to grow and develop like a tree until it produces poisonous fruit, resulting in the death of the target of the poet’s wrath.

In the first stanza, we’re introduced to the idea of emotion, specifically wrath, being something that can grow and develop like a living thing. The poet first compares the wrath he feels for a friend with the wrath he feels for an enemy. With the former, he is able to put aside his wrath through communication, but with the latter, his refusal to address it causes it to grow. As the poem continues, the poet “waters” his wrath through fear, tears, smiles, and deception. Eventually his wrath, comparable at this point to the tree of the title, bears fruit. His enemy sneaks in one night to take the fruit, and the next morning the poet “glad[ly]” finds his enemy dead from consumption of the poisonous fruit.

The rhyme and rhythm of the poem create an overall sing-song feel, conveying a lightheartedness for a topic that is actually quite sinister. The poem’s extended metaphor continues this feel. For me, at least, the overall effect that I get from all three elements is one of an unrepentant sinner, who gladly sings with almost childlike happiness over the murder, or at least death, of his enemy.