Which figure of speech do you find in the expression“Time is money”?

Metaphor is a figure of speech that, for rhetorical effect, directly refers to one thing by mentioning another.
It is an implicit comparison between two different things.
Usually ‘as’ or ‘like’ is used for the purpose of explicit comparison in a simile, but ‘as’ or ‘like’ is not used for the purpose of metaphor.
For example, “Liza is a rose”.

Metaphor is an implicit comparison between two different things.
Example-
- Time is money!
- Life is but a walking shadow.
- My life is local bus.

Source: An ABC of English Literature, Dr. M Mofizar Rahman.