Looking out of your window in the morning, you notice that all the flowers in your garden are missing.
What happened? You take a guess at it:
"A rabbit might have eaten all my flowers."
Let's take a look at that form.
might (modal) + have + eaten (past participle verb)
We use the modal might (you can also use may or could) because they show that we are not 100% sure about what happened. We are speculating about past events (guessing what we think happened). We then must use have followed by a past participle verb. We use 'must' when we have a stronger opinion about what happened.
Here are some other examples:
"My neighbour could have stolen the flowers"
"The wind might have blown them all away."
You can find more information here: Speculating about past events