You can’t get a material directly from an Actor, because the Actor could contain multiple Components, each with multiple materials. You can ask a specific component for the material on a specific section though.
When you perform an overlap you can Cast to whichever actor is being overlapped, and then get the variable of the component you want out of that actor, then get the material of that component.
For trace hit you can get the component and physical material together with the actor in Break Hit Result directly so it’s even easier.