A metaphor transfers the meaning of one thing to something completely different. Its name, in fact, comes from the Greek word "metapherin," which means to transfer. Unlike a simile, which suggests one thing is "like" another thing, a metaphor states that one thing "is" another thing. For instance, "Their marriage had become a prison," would suggest to the reader that the marriage had taken on the characteristics of prison without actually becoming a literal correctional facility.
Symbols are in fact tokens that indicate that one thing takes the place of something else, and consist of words, images or phrases used as a substitution for a more literal or figurative description. For instance a flag denotes patriotism, whereas a cross may indicate Christianity. In literature, writers use symbolism to interject these images through the written word, for example using roses to describe beauty or love, or animals to describe character and emotion.
Whereas symbols are figurative or literal place marks for an idea, a metaphor generally compares dissimilar ideas by making them one and the same. Symbols can also be used conceptually, such as an ongoing theme throughout the narrative. In "Star Wars," the Force is used as a spiritual symbol of the battle between good and evil. In the movie "The Sixth Sense," filmmaker M. Night Shyamalan uses the color red to connect the physical world with the spiritual world.
Because symbols are tokens for objects, symbolism can be found in metaphors for an instantly recognizable object. In the sentence, "She saw red," this metaphor uses color symbolism to express profound anger. In "Cast Away," the lead character played by Tom Hanks is faced with a literal crossroads at the end of the movie, an easily recognizable symbol that also doubles as a metaphor for his reaching a crossroads in his own life.