The Soccer Match is an Easter Egg in Halo 5: Guardians found on Mission 4 of the Campaign named Meridian Station.
Activation
To activate the Soccer Match, enter the Meridian Station. You must walk past Governor Sloan's hologram and stick to the road on the left. After passing two buildings, you will come across an odd shaped building covered in green tarp on the left. There will be a bright orange Vending Machine in front of it.
Once at the Vending Machine, you will be able to select a button to Activate it. Continue to activate the Vending Machine multiple times until you hear the sound of a sports whistle and a cheering crowd. Once activated, to the left of the Vending Machine a Soccer Ball will spawn near a yellow Mongoose.
Locke will challenge Buck to see who can score a goal first.
Once in possession of the Soccer Ball there will be two goals made up of Traffic Cones near the back of Meridian Station near the large security door. One goal will be on the large security door, and one across from it in front of a Barrier.
Score both times to set off the Grunt Birthday Party sound, and fireworks.
Trivia
The Soccer Ball has been a long-time easter egg and Forge item in the Halo franchise.
Gallery
.jpg "Soccer Ball (Halo 4).jpg (165 KB)")
Video
Halo 5 - Soccer Easter Egg