Screen optimization for all monitors and resolutions

Currently, in my game, some resolutions, create these black bars, which happen to block up some of the view of the game. Is there a way (preferably, without scripting) to solve this so that no matter how wide or tall a player's monitor is, they can play it the same way another player can?

Btw all the UI is fine, it's just that the actual game.

Oh and also my game is 3d first person.

Thanks for any suggestions!