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 have a face like a wet weekend.
If you have a face like a wet weekend, you look very unhappy or miserable.
E.g. Poor Simon has been walking around all morning with a face like a wet weekend. Apparently his girlfriend dumped him at the weekend.
(To be) like a kid with a new toy.
This is used to describe someone who is (excessively) excited about something. It’s usually, but not always, an object they have got / acquired.
E.g. Whenever he gets a new phone, he’s like a kid with a new toy. He never puts it down!
Have fun learning English!
Louise