We're Burning Sunshine
From Halopedia, the Halo wiki
We're Burning Sunshine is a Halo Wars Bonus DVD exclusive song. It can be heard in the cutscene where Red Team battles Honor Guard Elites and John Forge battles the Arbiter. It also plays on the first level where the player takes out Covenant forces around the base to take it back, combined with Just Ad Nauseum. It runs for a total of 2 minutes and 43 seconds.