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 be) like pulling teeth.
This phrase is used to describe something that is very difficult, tedious, labourious and / or takes a lot of effort to get it done.
E.g. It was like pulling teeth getting the board to agree but we persuaded them in the end and the budget has finally been approved.
Like night and day.
If two things are like night and day, they are completely different.
E.g. Compared to last year her school grades are like night and day. She has really made an effort to study hard and her grades have improved a lot.
Have fun learning English!
Louise