what do you do with skulls after you find them in Halo 3?

[Tyler]

I found a skull in halo three, but I pick it up and nothing happens. What do I do with it

 

[bluegravy]

Just play the dam game and you will find out.Thats how i did it.

 

[Shikamaru]

In the menu (outside the campaign, like when you start up the campaign game) you can turn them on to add a challenge or fun to the game, depending on which skull you got. Gold skulls add challenge, silver skulls add fun.

 

[Brendan]

Also, by turning on your skulls you can activate challenges which in turn give you multipliers to your score if your aiming to get certain single player achievements.