Some poems have hidden meanings. Sometimes the meanings can be significant, sometimes light. Here is an example poem with a light hidden meaning:
the sentry stood
as all did leave
after the sun did climb
only sticks and stones remained
This poem might sound significant, but the hidden meaning is light. This poem is about a snowman melting. The snowman is the sentry. The family at the house where the snowman is, left for the day. As the day warmed up, the snowman melted. All that was left were the sticks for his arms and the stones for his face.
The idea of having poems with hidden meanings brings up a number of ideas, some of which are examined below.
Significance to the insignificant
Sometimes when a poem has a hidden meaning, the poet can impart significance to something that is otherwise insignificant. Think of a poem about a brown leaf falling from a tree. This, in itself, is insignificant. A poet though, could apply a metaphor of death to this idea and write a poem portrayed with depth and meaning. The underlying meaning of the poem is not that important, but the poem is portrayed with importance in it.
Insignificance to the significant
On the reverse, if a poet writes a poem with a hidden meaning, they could take a significant idea and write a poem that seems insignificant. For example, a poet could want to write about birth. This is something significant. They could though portray this idea by writing a poem about a package that was delivered. The delivered package could symbolism the birth. In doing this, a poet would be writing a poem that seems insignificant, but about a significant idea.
Expression without revealing
One reason a poet might have a poem with a hidden meaning is that it allows the poet to write about something without being overt. A poet could express themselves without revealing something about themselves.
There are a number of examples that this could apply to. One example might be a poet wanting to write about an addiction that they have. They might want to express themselves, without revealing that they have an addiction. They could do this by writing a poem with a hidden meaning.
Tricking the reader?
One issue that can come up when writing a poem with a hidden meaning, is the issue of tricking the reader. Some might perceive a poem with a hidden meaning as not being honest with the audience for the poem.
As an example, consider a poem that is on the surface about a light bulb burning out. If this poem was really about death, this might seem to some as fooling the reader.
Even more so, a poem that is on the surface about death, but really about a light bulb burning out, might seem disingenuous to some readers.
Another issue that comes up with poems with hidden meanings is the idea that, unless it is done, the poems have no explanation. The reader might not ever know the poem had a hidden meaning. The reader might take the poem at face value. If for some reason, letting the reader know the poem had some sort of other meaning was important to the poet, this could be an issue.
Use of metaphor and symbolism
One benefit of writing poems with hidden meanings is that they can be a good exercise in the use of symbolism and metaphor. Trying to hide an idea while still expressing it can be a good way for a poet to learn about writing poetry.