I dont know a lot about sound desing, but I think this question has to do with it.
When you hear deftone's - change in the house of flies, how do they get that kind of whinny dark sound in the background? I dont know how to describe it, but its the one that starts at 00:08 Does anybody know how to get that sound?


If you know how to create that sound or know how to make other dark sounding type of sounds or effects, or can post other examples of cool stuff like this that you can do and incorporate in music, please let me know! Thank you in advance.
It'll be a synthesiser of some sort. Check out some of the DSK synth plugins, they're free and Synthtopia or Darkness Theory might be able to do something like that.
Deftones use a ton of synths for effect; odds are that if you don't know how they get a sound, it's a synth. In this case it's an ambient sound; it might not have been made on a computer since it's from 2000, but try subtractive programs like NI AbSynth to get slow-attack pad sounds.