If you have kids, particularly boys, you may have a wall or two that looks like this-
I found this lovely hole hiding behind a bookshelf in my boy's room. I'm guessing someone took their tantrum out on the wall with his foot. Haha! No problem, it's an easy fix!
Can you see the layers of color? Haha! I see lime green! This room used to be the dragon fly room before I re-painted the whole thing a creamy sage a couple years later.
Okay, so go buy one of these metal wall patches. I bought mine at Home Depot for like $4 or $5. Literally just peel and stick. Make sure the mesh side is facing you.
Next, you'll need some joint compound. I usually have a big bucket of this stuff handy (it's way cheaper to buy a large amount), but you can buy these little ones for about $5. It's enough to patch quite a few big holes.
This part's like frosting a cake. Just take your joint knife and spread a thin, even layer across the metal plate. Let each layer dry before sanding and applying the next coat. I did 3 coats. You can't tell in this picture (because I cropped it), but my finished patch is about 3 inches bigger all the way around than the metal plate itself. Let it dry and sand it smooth.
If you're patching orange peel-textured walls, buy a can of spray texture. I set the dial somewhere in the middle. It sprays a little chunkier than you expect, but it's ok. Practice outside on a box or something until you get the right texture. Once it's dry, lightly buff over it using your sandpaper. Not enough to where you're taking the texture off, just soften it a little. Finish with a couple coats of paint. That's it! Good as new! Except now, you can stick a magnet to the wall in that spot! Cool! :)