The gameplay in "Halo 3" is similar to the gameplay in "" and "Halo 2" but with added features. It is a first-person shooter that takes place mostly on foot but with sections that have vehicles the player can drive. A player can carry a range of weapons including sniper rifles, rocket launchers, grenades and alien weapons such as "beam rifles" and "needlers". Unlike the old games, during multiplayer all weapons a player is carrying can be seen on the player. This includes side holsters for pistols and larger weapons that can be slung across the players back. "Halo 3" also introduces 'support weapons', large two handed weapons that slow the players movement but do a lot of damage. Two examples include the flamethrower and a heavy machine gun, which are new to "Halo 3". The game also included a map-editor called "forge" where players can create their own arenas and battlegrounds to fight in. Almost all weapons and objects in a level can be moved or deleted in forge mode. The game also has "theater" mode which lets players record some of their best kills or plays from multiplayer mode. The last 20 games played are automatically saved, although this feature needs an Xbox 360 hard drive to work. These movies can be uploaded to Bungie's website where other people can download them and watch them on their PC.
"Halo 3's" story mode contains nine levels. It finishes the story of the "Halo" trilogy. The story can be played alone, with a friend on the same console or with four players over Xbox Live. The first player takes control of Master Chief, the second player plays as the leader of the Elites, "Arbiter" and the last two as elites themselves. There are skulls hidden through the levels. If they are found by any of the players the gameplay changes in some way. For example one skull makes confetti and balloons appear when a player gets a headshot and another makes all enemies stronger and tougher.
A multiplayer game can have up to four people on one console, or up to sixteen players over Xbox Live. There are many different types of multiplayer games. There is a death match, where the goal is to kill all the players (called "Slayer" in Halo). There are capture the flag games with two teams (eight people on each team). In capture the flag, each team has their own flag. The goal of the game is to steal the enemy flag, and take it back to base to score a point. Aside from these there are also team games. These games can have two, six, or eight players on each team.
There is a ranking system in Halo 3 that matches players with other players of the same ability, to make sure it is a fair game. The ranks are based on real life military ranks. The lowest is corporal but players can progress all the way up to general. Because multiplayer Halo is often played online there is a mute option, which lets any one player blank out the voice of any other player if they are being insulting or annoying.
The game is set in the same fictional world as the rest of the Halo series. Most of the game takes place in the future year 2553, over 500 years from now. In the storyline humans have developed faster than light travel, and now live on many planets and moons of the Solar System. When humanity started to build another settlement on a planet around another star they met the alien "Covenant". The Covenant declared religious war on humanity. During Halo 2 the Covenant discovered Earth. At the start of Halo 3, the Covenant are launching a full-scale invasion of Earth.
The Halo of the games title is the name of a series of space super weapons built by a mysterious race called the Forerunners a long time before the game. The Halo's are the last defence against another alien race known as "the Flood". The Flood want to use every living thing in the galaxy for food. The Halos are actually giant super weapons, that when activated, will kill all life in the galaxy. This is the only way to stop the Flood,to starve them by killing all their food. The Covenant do not know this and are attempting to fire Halos as part of a wrong religious prophecy. In the first Halo game, , the humans and Master Chief manage to stop the Covenant from firing one of the Halos. They also destroy one of them in the process. The destruction of one of the Halos starts an emergency. The Halos can now "all" be fired from one place, using a device called "the Ark". The Covenant, still not understanding the truth, launch an invasion of Earth, where they believe the Ark is buried. This is where the "Halo 3" story starts.
The main character of "Halo 3" is Master Chief. Master Chief is a super soldier, the last surviving member of the Spartan Project. The Spartan Project was started by humans to genetically, using genes, make soldiers who were stronger, faster and tougher than any normal human. Another character from Halo 1 and 2, controlled by the second player in a co-op game is "Arbiter", the leader of the alien Elites. In "Halo 2" he is an enemy but in "Halo 3" he joins forces with the humans. Other returning characters include the veteran human soldier Ser"geant Avery Johnson", the AI "Cortana", the robot "343 Guilty Spark" and "the Gravemind", the dangerous leader of the Flood.
"Halo 3" begins where Halo 2 left off. The player once again plays as Master Chief as he falls towards Earth. He crashes in Kenya near the city of Mombasa. He is found by a squad of marines led by sergeant Avery Johnson, the commander from Halo and Halo 2. The player and the marines fight their way through invading Covenant force to a human outpost. Here they find human forces making a last attempt to stop the Covenant from activating a portal they found buried in the Kenyan desert. They are unsuccessful however, and the Covenant open the portal to the Ark, where they will be able to fire the Halos and destroy the galaxy.
Just after the Covenant fleet of spacecraft leave the portal, a big ship crashes into the city of Mombasa. This ship has been taken over by the Flood. The player as Master Chief, must fight their way into the ruined spacecraft and recover the robot Cortana who can tell them the way to re-open the portal and follow the Covenant. Once the player is successful, the humans re-open the portal and head after the Covenant to stop them firing the Halos. Joining them is 343 Guilty Spark, one of the robots who helped build the destroyed Halo from the first game. Once through the portal the player and his allies discover the huge, planet-sized structure known as the Ark, where all the Halos can be fired from. Led by 343 Guilty Spark the player makes their way to the centre of the Ark where the Covenant leader, the Prophet of Truth is preparing to fire.
Just as the player arrives to stop the Prophet of Truth, the Flood infested ship "High Charity", arrives in an attempt to take over the Ark. The player, Arbiter and Johnson now take out all the Flood in the area before Arbiter kills the Prophet of Truth and prevents the Halos from being fired. There is no time for the player to rest however, as he must now head to the nuclear reactor at the center of the Flood infested spacecraft, "High Charity" in an effort to kill the Flood. Once this is complete, the player and Arbiter must go and activate "one" Halo ring. This will destroy the Ark and kill all the Flood in this area of the Milky Way Galaxy whilst saving the rest. The player and the Arbiter head off to activate the single Halo and save the Galaxy.