Handling symbolism in fiction can be pretty tricky. But when done right, it can enrich your fiction in wondrous ways. Throwing it in just to have it in there can be done, but I don’t recommend it. If a certain line from a famous poem keeps showing up, then it better damn well have a connection to the story’s plot or theme, or to a main character. Otherwise, it’ll just be redundant and annoying.
You also have to avoid the danger of getting too esoteric. After all, it’s pointless to fill your book or film with hidden messages if it goes over the head of the majority of your audience. But then again, if even one person in the theater during a showing of Transformers: Revenge of the Fallen jumps up and yells “Jesus Christ has chrome!” when Optimus Prime is brought back to life, then maybe you did your job right after all…
Symbols are also good for foreshadowing later scenes. Like the old saying goes: if you show a gun on a table in Act I, then it better get used by Act III—or something like that. The point is symbolism needs to be more than just symbolic; it needs to fit within the overall structure of the story. Otherwise, all you got is useless fluff. And nothing in your story should be useless—ever. If you like useless, then go write literary and call yourself an aaaaaahhhhtist. Or better yet, learn how to write a real story so you don’t have to.
So yeah, symbolism is cool (Hehehehe, yeah! Cool!). But only when it isn’t overdone and only when it actually matters.