What are the purpose of these messages in Revelation?
So that we will learn that God is the Righteous judge. And that you can't bribe God thru your good works.
The interpretation of Locusts - the army of demon.
Revelation 9:4 They were told not to harm the grass of the earth or any plant or tree, but only those people who did not have the seal of God on their foreheads.
All believers have the seal of the Holy Spirit and during the judgement and we are spared from these locusts. We have protection because Christ is in us.