The sun represents a rebirth. The children wait for the sun, and when they see it they understand how cruel they have been to Margot.
A symbol is something that stands for a larger idea than itself.
In “All Summer in a Day” a group of kids living on Venus are waiting for the sun to come out. They are annoyed at one of the girls there, who has come from Earth, where there still is a sun. So they lock her in a closet.
Before the sun comes out, the rain stops. The most pressing thing about it is the silence.
The silence was so immense and unbelievable that you felt your ears had been stuffed or you had lost your hearing altogether. The children put their hands to their ears. They stood apart. The door slid back and the smell of the silent, waiting world came in to them.
Next, the sun comes out. This is the incredible sight they have been waiting for.
It was the color of flaming bronze and it was very large. And the sky around it was a blazing blue tile color. And the jungle burned with sunlight as the children, released from their spell, rushed out, yelling, into the springtime.
The children have expected seeing the sun to change their lives. In a way, it does. They come to understand that they have locked Margot up so long that she missed it, and this is a terrible thing to do. Although the story does not explicitly say what happens, we know they feel guilt.
They turned through the doorway to the room in the sound of the storm and thunder, lightning on their faces, blue and terrible.
They regret what they have done to Margot. They understand that they have been terrible bullies.