An allegory is a narrative in which a component, such as a character or setting, is representative of a particular value or underlying idea. A metaphor is a figure of speech wherein an unfamiliar subject is described using an attribute of a familiar subject. Both allegory and metaphor also make great use of symbols. Although allegory and metaphor are often used interchangeably, they are not strictly one and the same.
Allegory and metaphor have key similarities, which is why a lot of people frequently mistake one for the other. Both are literary devices that make use of rhetoric. In general, an allegory can be more accurately considered as an extended form of a metaphor. Metaphor deals with only a singular idea or symbol, and typically consists of a single phrase or sentence, while an allegory tells a complete story that consists of different symbols related to one another. William Langland’s Piers Plowman and Nathaniel Hawthorne’s Young Goodman Brown are examples of allegories, while the plays of William Shakespeare and the poems of John Donne are rich in metaphors.
Learning the different components of both allegory and metaphor will help people understand the difference between them. A metaphor is a figure of speech, just like a simile. Metaphors and similes are almost the same except that similes make comparisons using the word “like” or "as". For instance, “her smile was like sunlight shining down on me” is a simile, whereas “her smile was sunlight shining down on me” is a metaphor.
With the metaphor “her smile was sunlight shining down on me,” the tenor or unfamiliar topic is the woman’s smile, which may be something another person has yet to see. To make it easier for the other person to visualize the woman’s smile, a familiar subject or vehicle is used in comparison. The writer is assuming that the vehicle he or she is using is familiar to all. When the writer makes a wrong choice of vehicle, a metaphor fails to make sense.
Allegories are often mistaken for parables and fables. Although all have similar functions and components, the main difference lies in their themes and use of symbols. Parables and fables typically have a single theme or lesson, and all symbols used in them are related to the lesson being imparted. Allegories may have more than one lesson to impart.