I recently received a Lenovo X1 Carbon Gen 3. Using this with xmonad, a lot of the special/multimedia keys do not work. Using other DMs such as Gnome or KDE take care of this and provides a built in utility to maps keys.
Using Xmonad I needed to map these myself, def a learning experience. Links below explain how to discover why a keypress sends to the OS, how to intercept it, and how to map it to an action.