Angels are "God's Messengers"

Angels are created beings. That's why they are not to be worshiped. Only the Creator is to be worshiped. They are immortal. They are not eternal because they did have a starting place. God created them...they do live forever. They are God's servants who carry out His business in the world.
Angels have one job...to serve God and do His bidding.

Psalm 103:20-21

Praise the Lord you his angels,
you mighty ones who do his bidding,
who obey his word.
Praise the Lord, all his heavenly hosts,
you his servants who do his will.

Angels obey His word; they do His will.
They're God's obedient servants.