“A metaphor is not language, it is an idea expressed by language, an idea that in its turn functions as a symbol to express something.” – Susanne Langer
Let’s go through a quick definition. A metaphor is a rhetorical device in which the traits of something are attributed to something else, but not in a literal sense. It helps to understand that a simile is a type of metaphor, so let’s take a look at an example:
“But look, the morn, in russet mantle clad, Walk o’er the dew of yon high eastern hill” – Hamlet, William Shakespeare.
The coming of morning is likened to being clad in a “russet mantle” (where russet is a red-orange tinted brown). Now obviously, this is not literal. Morning does not wear any clothing. The russet mantle is a metaphor for the rising sun and the colour of dawn.
Let’s look at symbols now. These are not used in rhetoric or discourse, and is usually a specific thing that represents some other thing or concept. Symbols, unlike metaphors, are not specific or definitive in their interpretation. They carry a wide range of ideas through generations in an almost meme like fashion. Because of this, the symbol’s meaning must be inferred from context. For example, anything long and roughly cylindrical can be considered a phallic symbol; whether or not it was intended that way depends entirely on the context.
Definition aside, this is what really helps me remember the difference. Metaphors are like similes, they liken the principle term to something else (whether it be a thing, idea or process) to endow the principle term with characteristics reminiscent of that which it has been likened to. A symbol is much more succinct; it can be a single thing (usually an object but not limited to one) that is not directly given meaning through comparison (like a simile/metaphor) but whose meaning is created by the context in which that symbol is used. Basically, that means I don’t have to explain a symbol because that’s for the reader to determine for themselves based on what’s been written, whereas a metaphor must be directly explained by the text.