"I, John, am the one who heard and saw these things. And when I heard and saw, I fell down to worship at the feet of the angel who showed me these things. But he said to me, 'Do not do that. I am a fellow servant of yours and of your brethren the prophets and of those who heed the words of this book. Worship God.'”
When John falls down to worship the angel, the angel rebukes him (this is the second time this has happened, for John did a similar act in Revelation 19:10). Angels are not to be worshipped. They are created beings -- created by God Almighty -- and to worship them is idolatry. When the angel Lucifer set himself up to be worshiped God cast him out of heaven (Isaiah 12:14-17, Luke 10:18). No doubt John knew this, but he was overwhelmed by what he had been shown and lost himself in praising the messenger. We can be in danger of doing this, too, if we become awed by those who deliver God's word in a sermon or message and put them on a pedestal. There is only One worthy of our awe and worship. Only One who is awesome. The Triune God.