There are many purposes for angels. They are messengers. Angels carry out and enforce God's will. They fight and deliver judgment and punishment. Angels attended and strengthened Jesus, and they give strength to and serve those who will inherit salvation.
Angels deliver, guard, protect, lead, make preparation, teach, and give insight and instruction.
They serve as witnesses. Angels praise God and worship His Son and rejoice when a sinner repents. They carry at death. Angels will accompany Jesus at His return. They will harvest at the end of the age, separate the wicked from the righteous, and gather the elect.