I think you mean "metaphor." A metaphor is a comparison of two things that are not normally similar.
You are my sunshine.
He is a pig.
The warm Spring weather was a tonic for my soul.
If you use the word "like" or "as" in your comparison, it is called a "simile."
The clouds were like cotton candy.
She cried as though her heart was being crushed by a mallet.
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