It is a idiom.
She's as wild as a tornado.
A simile.
A metaphor
It is a simile.
As quick as a wink is a simile. ----
The literary term is simile. A simile is a figure of speech that compares two unlike things using "like" or "as". In this line, "Like heath that in the wilderness The wild wind whirls away", the comparison is being made between the heath and the way the wind whirls away.
simile
simile its a simile when you use "like"
simile It is an example of a simile (uses like or as). A simile in itself though is a type of metaphor.
simile
The door flung open, like something wild had escaped from it . Like it was empty, two-story tomb of some runaway zombie.