The pharaoh was the high priest of every temple in Egypt. His job was to maintain maat through carrying out the daily religious rituals. As he could not be in every temple, he delegated this task to the priests. But, as the high priest, the pharaoh was often shown carrying out the rituals and making offerings to the gods.
The wall fragment here from the temple of Hathor at Kom Abu Billo shows Ptolemy Soter I presenting nu pots to Hathor.