Like many other real-time strategy games, Age of Mythology is based on defeating enemy units and towns, building your own units and towns, and training villagers and fighters. In this way, players are able to defeat and conquer rival towns and civilizations. Players advance their tribe through four "Ages": starting in the Archaic Age, the player may upgrade to the Classical Age, the Heroic Age, and finally, the Mythic Age. Each upgrade to a higher Age unlocks new units and technologies for the player, which strengthens their settlement. However, upgrading requires a sum of resources to be paid and a certain prerequisite building to be constructed.

There are three playable cultures in Age of Mythology: the Greeks, Egyptians, and Norse. Each culture has three "major gods"—important deities such as Ra, Zeus, or Odin. The player chooses their major god before the game begins. Every time a player advances to the next age, a "minor god" is selected. Minor gods are slightly less significant historically than their major counterparts. Some minor gods include Bast and Aphrodite. All gods grant the player unique technologies, myth units, and a unique "god power"—A one-time special ability that can either damage an opponent, or benefit the player that uses it.