Which figure of speech do you find in the expression -“Life is but a walking shadow”?

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”.
Source: Britannica