Whats the underlying message or idea in a literary work

Theme differs from the subject of a literary work in that it involves a statement or opinion about the subject.

the black night was split open like the coconut

it says that it was totally black in the mind of a person but suddenly his mind opened like a coconut with the sweetness of the coconut water and the white color inside it.

or

the black night was thrown like a coconut and it slit apart with its sweet water coming out .