The player navigates through several missions based on stages from Metal Gear Solid 4, each introduced by brief text summarizing the story so far. The player moves their finger across the screen to aim, tapping to fire, and moving their fingers together or apart to zoom in or out with a sniper rifle, removing their fingers from the screen to get behind cover and avoid enemy fire. The main character's primary weapons, an assault rifle and a sniper rifle, can be rotated with one another by pinching the device's screen.
The player plays as Solid Snake, who is also known as Old Snake in Metal Gear Solid 4. The entirety of Metal Gear Solid has been streamlined into a portable and more accessible form. The main objective of most missions is to kill a set number of enemies. Enemies include hostile PMC soldiers, Haven Troopers and Gekkos, which are unmanned fighting machinations. There are also friendly targets which the player is penalised for shooting at. Some sections contain 'Boss fights', where the player fights a boss from the Metal Gear Solid 4 storyline; e.g. Laughing Octopus.
Unlike in Metal Gear Solid 4 where the player has a camo index, where they sneak around the map. In the revamped streamlined version of the game for iPhone, the camo index is removed completely. Instead the player is given baricades to hide behind for cover as they shoot enemies and reload. Similarly to other games in the Metal Gear Solid series, at the end of each mission, the player is awarded a rank based on their precision and speed in completing the mission. Higher ranks award more Drebin Points, which can be used to buy rewards such as iPhone character wallpapers.