The enemy when he comes against you fires his weapons. Goliath laughed first, he then changed and started using powerful weapons. He thought he had the upper hand but somehow got serious-that's interesting. A spear and a little boy. I think his demon was really responding and not Goliath himself.
The devil knows David was really a supreme force as God was his faith and the word of God was on his tongue.
We may find the devil contesting and trying to sift us. We must resist fear and bombard him with the positive word of God. example-- when the enemy comes in like a flood (philistines) the Lord will raise a standard against him-- we should confess many promises as well as the blood. Especially when we are hurting, he is not playing neither should we. The word is more powerful than all nuclear put together.