"She really ruffled his feathers" this is a metaphor, because we are talking about a woman annoying a man - not about a woman stroking a bird.
"The moon's a balloon" is a metaphor - of cours the moon is not really a balloon
"The world is my oyster"
"She was a tigress when roused"
Similes and metaphors can be very similar, but you must remember the definition. You cannot substitute "comprable to" because you are not comparing, you are actually saying that one thing is like another.
Languages are not always logical, because they are full of idosyncratic things - like metaphors, similes, idioms and proverbs. Can you think of an idiom or saying in your language that an English speaker might not understand?