Zippers are a such great fastener. The work for so many things like backpacks, dresses, jackets, jeans, etc. They can be long or short, any color, and some are even decorative.
To fix a metal zipper you need a metal zipper repair kit. If the zipper pull is broken but still on the zipper, then cut off the bottom zipper stop with either scissors or the nippers.
The prongs will come through the fabric to the back of the zipper. Fold all the prongs down to secure the zipper stop to the bottom of the zipper.