There are many expressions commonly used in English with the comparison form ‘as … as’.
There is no magic rule to help you remember them. You just have to learn them. Sorry!
Take a look at the examples below.
As quiet as a mouse.
If someone is as quiet as a mouse they are extremely quiet and making very little or no noise.
E.g. She was as quiet as a mouse as she moved around the house. She didn’t want to wake the baby.
As right as rain.
If someone or something is as right as rain it means that things are exactly as they should be. The person is in good health and fully fit; things are working and running well.
E.g. I broke a bone in my foot last month. The doctor told me I’d be as right as rain in just a couple more weeks.
As sick as a dog.
If someone is as sick as a dog they are very unwell. It’s often, but not only, used with reference to stomach problems.
E.g. The last time he ate shellfish he was as sick as a dog for 2 days.
Have fun learning English!
Louise