How many groups are angels divided into? What are their duties?

Only Allah knows the number of angels. There is no clear information about the number of angels in the Qur’an and hadiths. However, it is possible for us to say that they are far more than we can count based upon hadiths. Moreover, according to the news given by the prophet Muhammad (PBUH); an angel comes to the earth with a drop of rain and its turn does not come again.