What is the difference between symbolism and metaphor ?

They're related, but generally a metaphor is used to draw a comparison between two distinct objects, whereas a symbol is used as a stand-in for a much more complex, and generally more abstract, idea. In literature, a metaphor would typically be used in a specific instance to compare two objects, but a symbol would be used throughout the work as a major part of the theme.
Taking into account the explanation, it seems to me the animals in the story?Animal Farmcould be different symbols.