How to Level Up in Modern Warfare Games

In modern warfare, there's like a really good variety to the way the guns work and the way you can customize them. I feel like in a lot of these games they have these meta systems that encourage you to play the game differently but often in ways that don't actually make you better at the game or a better teammate. And I'm really looking forward to eventually seeing some side missions or some meta structures in these kinds of games that push you to actually become a better player of the game.