Mary: John, can you come to Matt's birthday party this weekend?
John: I'm sorry I can't. I have been very tired these few weeks and I just want to rest.
Mary: What have you been doing lately?
John: I have been working every day, and in the evenings, I have been studying for an upcoming Japanese test in 2 weeks’ time.
Mary: Wow! You are as busy as a bee.
The words in bold are called "similes" (直喩). They are English expressions that you use to describe someone or something common to another thing that comes to your mind.
For example, lions are known to be brave. If you want to describe a person very brave you would say:
Sam is as brave as a lion.
Another simile expression we use is with "like". This more describes the action.
Jane can swim very well. We would think of a fish as to swimming.
So, we can say:
Jane swims like a fish.