Can anyone help me with Halo 3?

[Aleksandar D]

Well i just bought Halo 3 for my xbox 360 of course because thats the only system halo 3 is on but anyways when i go online i can play with my friends(live) but idk how to find public matches because my friends dont always play and they might not always want to send me an invite.I just dont know how to play with random people so i can rank up. Is that because i didnt pass the game? If you have to pass the game to play with anyone can you pass it on co-op or does it have to be solo?Please help me someone.

 

[DJ94]

When you go on to the main menu, go into "Matchmaking" and then you choose what game type to play etc