Seven angels had seven plagues and when they received these plagues, something happened in the temple in heaven,

The temple was filled with smoke from the glory of God and from His power, and no one was able to enter the temple till the seven plagues of the seven angels were completed (Revelation 15.8).

Smoke filled the tabernacle of Moses and the temple of Solomon, but here the actual temple, of which the tabernacle of Moses and the temple of Solomon were only copies, filled with the glory of God, seen as smoke by John.

Can you imagine that sight? Wow! John knew that something big was on its way.