Broken Drywall on Corner of wall
The corner bead is there purely to create a nice corner edge. It does not support anything: it is purely a cosmetic feature that everyone uses instead of trying to create a perfect edge freehand. When you place it on an outside corner, the bead sits a bit above the level of the drywall such that you can slap joint compound on the bead, and then smooth it out easily using the bead and the flat drywall surface to create a seamless, sharp edge. It also provides a stronger, longer-lasting edge than plain joint compound.
If the bead is undisturbed and only the wing of the corner bead is disturbed, then you can fill the hole with joint compound/spackle, and use that bead as an edge to create a flat, smooth surface. Make sure all the metal is below the level of the bead and the wall.
If the bead, itself, is bent, you can still use spackle or mud (joint compound) to re-create the corner.
If it is all messed up, you can either tear it out of the wall and replace it with a new piece of corner bead or cut it just above and below the damage and replace it with a segment of corner bead. It should be nailed into the studs, so it will take some yanking. Corner bead is cheap, though, and makes repair work easy.
All repairs will require you to paint after you repair it. If you use joint compound, then you need to prime before you paint. Some spackle is self-priming, allowing you to just paint directly on it.
[This message has been edited by Lawrence (edited October 28, 2002).]