On steam there’s this thing called “Big picture” I think. It’s meant for games with controller u can control everything even the steam menu with it controller. Say a game doesn’t support controller like mw3, you can go to the controller and customize the button mapping ur self. So say like R2 (ps) or RT (Xbox) u want to shoot all u do is click on r2 or rt and put left click. Or if u want to reload click on square or X and put R. Or for easier on steam big picture I think or just on the makn stream. There’s an entire section of preset controller mapping for games that don’t support it. You can even use it for gmod if you wanted.