The Angel has 'the rainbow
on his head'.
The Greek says "the",
not "a",
indicating a particular
rainbow.
The rainbow is seen in the fourth chapter as a part
of the throne of God.
The rainbow concerns the covenant God made with
Noah not to destroy the earth (Genesis 9:11-17).
This shows that though Christ will deal out judg-
ments, they will be a cleansing, preparing the
earth's regeneration, not to completely terminate it.