Matewis: Uhm, lorewise or gamewise? I'm not as clued up about 40k's lore as I'd like to be, but from what I understand their soldiers are pretty weak individually, but they make up for that with their large numbers and powerful vehicles. What are those sayings? Something like "The imperial guard is the emperor's sledgehammer" and "The space marines are the emperor's scalpel"
The Imperial guard are more like the "emperor's meatshields". Their strategy is pretty much: "We have more soldiers than they have ammo. Charge!"