If i have Map Packs for any game, and my friend doesnt have it, what will happen?

Depends on the game. Can you be more specific?

@aphilotus i edited it

Most games won’t let you play together.

At least in Halo 3, if all players set to play don’t have the map, that map is not an option for that game. So no, if you had, say the Legendary Map Pack, you couldn’t play any of those maps with your LMP-less friend.

Specific to your question, I believe that the map rotation for that game limits itself to the maps that everyone has, to prevent just such an occurrence.

I don’t playCoD, but I bet it is the same for them too. No pack, no play.

@aphilotus oh, ok.

For most PC games, the person who doesn’t have the map will download it from whomever is hosting the server.
This is probably true for xbox as well.

@Sarcasm XBox Live is all about making money, not sharing data!

@aphilotus True