Best practises for the iOS HUD

When would and when wouldn't it be appropriate to make use of a HUD? With both the HIG and Material Design not mentioning this topic I'm struggling to justify when it should or shouldn't be used.

Examples of the HUD I'm referencing are the volume change view and the "added to library" view in Music. An example image from a library: https://github.com/JonasGessner/JGProgressHUD/raw/master/Examples/Screenshots/Presentation.png