What does the sky do for us?

Contains our atmosphere, allowing us life on earth. Without the sky, we wouldn't be here.

answer 2 The blue sky that we see above us is a bit of an illusion, for the blue colour is just the scattering of light by dust particles in the atmosphere.

In response to the first answer, it is gravity that keeps our atmosphere close to the Earth.

But the Earths magnetic field also plays a part by resisting the effects of the Solar Wind, which would otherwise strip some of our atmosphere away.