If you are looking to build an army or learn the lore, these are the primary "Warriors" that defend Holy Terra:
The "Hammer of the Emperor." A massive force of ordinary humans using tanks, artillery, and sheer numbers to hold the line. Warhammer 40k - Warriors of the God Emperor
To start your journey as a loyalist commander, follow these steps: 1. Choose Your Playstyle Emperor of Mankind - Warhammer 40k - Lexicanum If you are looking to build an army
The "Angels of Death." Genetically enhanced warriors organized into Chapters like the Ultramarines and Blood Angels. Warhammer 40k - Warriors of the God Emperor