There are many expressions commonly used in English to express similarity.
There is no magic rule to help you remember them. You just have to learn them. Sorry!
Take a look at the examples below.
To drink like a fish.
If someone drinks like a fish, they consume large amounts of alcohol on a regular basis.
E.g. It wasn’t surprising to hear he was drunk at the party. He drinks like a fish!
Eat like a bird.
If someone eats like a bird, they consume very small amounts of food. (The phrase evokes the image of a bird pecking at its food and only taking small amounts each time.)
E.g. She is very slim because she has always eaten like a bird.
Have fun learning English!
Louise