For non-native speakers of English, poetry provides a special challenge. This is because it is a hallmark of poetry to jolt readers' awareness through the use of unusual words and syntaxes, as well as punning and idioms. Poems can make comprehension difficult precisely because poets are deliberately not following prose language norms.
An example of the kind of reversed syntax poets often use for effect can be found in Walt Whitman's fairly accessible poem "Song of Myself, V," in which he writes:
And limitless are leaves stiff or drooping in the fields
Normally in English, sentences begin with the subject, followed by the verb, a pattern EFL students will have learned. "Limitless are leaves," with "leaves," the subject word, being placed behind the verb, and the modifier "limitless" leading the way, is a syntax that non-native speakers are apt to find confusing.
Likewise, idioms and contexts that are completely familiar to a native audience can cause confusion to a person from a different culture. For example, if we look at T. Bone Slim's "The Mysteries of a Hobo's Life," we read:
I grabbed a hold of an old freight train
And the mysteries of a hobo's life
If one does not know what a hobo is, and I have had non-native students who do not, this poem is incomprehensible. I have students who have looked up the word hobo but still don't grasp the social and historical context of what that word conveys. Second, in the first line of the poem above, "I grabbed a hold of an old freight train," a non-native speaker is likely to be confused by the dialect "a hold" and wonder what the "a" is doing there. In a broader sense, too, the concept of grabbing hold of freight train is likely to be literalized by a non-native speaker and simply not make sense: how can a person grab hold of a train?
In general, when teaching poetry to EFL students, it is important to do far more preparation, plan to spend more time on a poem, and try to put oneself in the students' shoes to try to anticipate problems that might arise.