Metal Gear Solid V: Ground Zeroes is more than a one mission game! You have a lot more to accomplish since the game contains a lot of depth and atmosphere, items to collect and elements to unlock.
In addition to the main mission, which already gives you a lot of fun thanks to the different possibilities and ways to play through it, you will be able to unlock several side-missions with some additional objectives for different gameplay experiences. After completing each mission, you will unlock other related challenges that you will have to accomplish in order to compete in the ranking leader boards.
In order to complete the game entirely, there will be some other goals such as collecting the XOF Patches or Chico's Cassette Tapes, which will also give you a lot of information about the mission and why you are there. Plus, it will also unlock some extra content.
Metal Gear Solid V: Ground Zeroes will hold you hostage for a long time!