Final answer:
The sentence is an example of a simile, which compares two different things using "like" or "as".
Step-by-step explanation:
The sentence "He was as brave as a lion." is an example of a simile. A simile is a figurative use of language that makes a comparison between two different things using the words "like" or "as". This particular simile compares a person's bravery to that of a lion, implying that the person is very brave.
Other forms of figurative language include metaphors, which also make comparisons but do so directly without using "like" or "as", and imagery, which creates a picture in the mind's eye through descriptive language.