I would most likely want to hear "The Truth" by Foster the People, mainly because the lyrics perfectly represent Master Chief's role in the game. I'll think of more songs later. What would you want to hear in Halo 5 Guardians' soundtrack?
[spoiler]inb4darudesandstorm[/spoiler]
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Skillet - It's Not Me, It's You The reason why is because it explains the Hell that Master Chief has been through most of his life, with being kidnapped by the UNSC, and just recently by losing Cortana.