If you're going to throw a metaphor into your work, it needs to be somewhat understandable. Take Animal Farm. We all know it was about communism. We can even say which animal was Stalin or Trotsky. Or in The Lord of the Flies, Piggy is civilized society. I get it.

Because otherwise it's going to confuse the audience, particularly if the metaphor isn't subtle. Last night I watched Wagner's opera of Tristan und Isolde, a story about two people who accidentally drink a love potion. Unfortunately Isolde is married off to Tristan's uncle, and eventually their love affair is revealed. After being injured in a duel, Tristan dies and Isolde mourns her loss.

Whenever Tristan soliloquized his difficult situation, on occasion an actor in a white uniform or a small child would appear on stage, walk around a bit, and then disappear into the darkness without uttering a line. They clearly were placed there by the current director and were not an invention of Wagner and are supposed to represent... something, but I had no idea. Duty? Innocence? I thought my ignorance was perhaps because I'm terrible at this shit, but during the intermission from overheard conversations I could tell no one else could figure it out either.

It's like when that wolf would randomly show up in Advent Children. The creators are clearly aiming for something, but it's so vague it's nonsensical and even destroys the flow of the narration now that the viewer is bewildered. Metaphors are great if they enhance the experience. Doing it like that is not. It's jarring and can actually upset the audience. Don't fucking do it, unless you want your entire work to be a giant mindfuck like Ulysses.