Friction generates intense heat that can literally weld parts together.
At its simplest, axle grease is a thick, heavy lubricant designed to reduce friction between moving parts in your vehicle's axle assembly. Unlike engine oil, which is thin and flows freely, grease is "viscous"—it's designed to stay exactly where you put it, even under extreme pressure and heat. axle grease
Grease acts as a seal, shielding delicate bearings from road salt, dirt, and water. Friction generates intense heat that can literally weld