Why do angels perform functions such as warding off harm from humans, bringing down rain, and building palaces in Paradise, even though Allah, glory be to Him, is capable of all things?

We advise the questioner to ward off obsessive whispers by diverting their mind from them, seeking refuge in Allah from them, and occupying their time with learning and beneficial deeds. The angels are servants of Allah; He employs them as He wills. Allah possesses ultimate wisdom in preferring and choosing some of His creation over others, and in singling out some of them with special merits. He is the Doer of what He intends; He creates what He wills and chooses.