Call of Duty 4: Modern Warfare is a single-player and multiplayer first-person shooter game.

The campaign follows two parallel storylines set in a contemporary world threatened by international terrorism and civil unrest. Players alternate between two protagonists: Sergeant Paul Jackson, a U.S. Marine deployed in the Middle East, and Sergeant John “Soap” MacTavish, a British S.A.S. operative involved in covert missions across Europe and Russia. Their operations uncover a conspiracy involving ultranationalist forces and rogue military elements that threaten global stability. Across both perspectives, the player experiences high-intensity firefights, stealth infiltrations, and cinematic sequences that frame the unfolding crisis.

Gameplay emphasizes a mixture of squad-based combat and scripted events. Missions are linear in design, but the game frequently shifts tone and objectives, from open battlefield skirmishes to night-vision stealth raids. Players carry two primary weapons and grenades, with firearms ranging from assault rifles and sniper rifles to shotguns and rocket launchers. Equipment includes flashbangs and claymores, and scripted segments introduce fixed heavy weapons or vehicle-mounted guns. The player relies on regenerating health, taking cover to recover between engagements rather than using medkits.

The multiplayer component offers competitive online play across numerous modes, including team deathmatch, free-for-all, search and destroy, and domination. Players earn experience points by completing objectives and eliminating opponents, gradually unlocking new weapons, attachments, and perks that customize loadouts. Killstreak rewards, such as calling in UAV reconnaissance, airstrikes, and attack helicopters, add a layer of tactical advantage.

Call of Duty: Modern Warfare - Reflex Edition adapts the same campaign and multiplayer structure to the Wii. This version retains the narrative and mission flow but employs pointer-based aiming and motion-sensitive inputs for shooting, melee attacks, and reloading. To accommodate the hardware, certain graphical features are scaled back, and some online options are streamlined, but the core missions and systems remain consistent with the original releases.