If the reader heeds the grammar, then the reader will unlock the poem, if not, the reader will remain confused by it. Poetry is built on grammar by its very nature of brevity. The poet utilizes grammatical conventions to present which means the reader must be aware of those conventions to interpret. The grammar of poetry is often called Literary terms which when examined are grammatical. A simile and a metaphor are the same except in their grammar.
Literary terms are grammatical in nature.
In reading fiction, the reader oftentimes gets lost in the complexity of the story and doesn't know how to find the essence. Start with the grammar. Locate the verb in the sentence then the subject and the object and immediately the conflict or plot is found in the verb, the characters are discovered in the subject and objects and the rest are just modifiers in the form of adjective and adverb words, phrases, and clauses. When I have a reader confused by the literature we just step back and analyze the grammar of a paragraph and miraculously the reader begins to see better. The subtly of non-fiction is built on grammar.