What is the difference between a metaphor and a simile?

Both metaphors and similes are examples of stylistic devices used to compare two ideas. The main difference is that similes use words such as "like" or "as" in their comparison, whilst metaphors do not. A simple example of a simile is the phrase, "she is as free as a bird." As you can see, the word "as" is used to compare the girl to a bird. The phrase does not intend to suggest that she is a bird, but rather that she shares their liberated character.Alternatively, an example of a metaphor includes "Life is a roller coaster." Here, there is no use of the words "like" or "as." Yet, it achieves the similar purpose of comparing two unlike ideas by insinuating that the literal ups and downs of a roller coaster are a figurative characteristic of life.