Which one is an example of 'Metaphor'

Metaphor is an implicit comparison between two different things. A metaphor is a figure of speech that is used to make a comparison between two things that aren't alike but do have something in common.
Ex:
- Her tears were a river flowing down her cheeks.
- She's a tiger when she's angry

Simile is an explicit comparison between two different things. Usually 'as' and 'like' are used in Simile.
For example:
- “He eats like a bird,”
- “He is as smart as a whip,” etc.

[Source: An ABC of English Literature, Dr. M Mofizar Rahman, Britannica, merriam-webster ]