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.
Like a bear with a sore head.
If someone is like a bear with a sore head they are extremely grumpy, irritable, bad-tempered or annoyed.
E.g. He’s always like a bear with a sore head in the mornings. Don’t try to speak to him until he’s had his coffee.
Like bringing a knife to a gunfight.
This expression indicates a lack of preparation or being inadequately equipped to deal with a confrontation or a challenging situation.
E.g. If you haven’t studied Law, choosing to represent yourself in court is like bringing a knife to a gunfight.
Have fun learning English!
Louise