This is the epiphany, the nature and mission of Christ is revealed to those three disciples in this transfiguration on the mountaintop. And it is revealed to those of us hearing the story after the fact. Jesus is the messiah, the chosen one of Israel, the salvation of all humanity.
But what does the identity of Jesus of Nazareth as the messiah reveal to us about ourselves? We most definitely are not the messiah, so we are unlikely to be joined by Moses and Elijah and be transfigured on the top of a mountain.
As with many of the stories we encounter in the Gospels, Peter’s responses tend to be the example that so many of us can relate to.