The ancient Egyptians believed that their king was a living form of Horus and that when he died he became a form of Osiris in the afterlife. Horus had been the state god since very early in Egypt's history. Even in pre-dynastic times, kings had a special "Horus Name" by which they were known. Royal names were written in a serekh (not the more familiar oval cartouche, which came along later) with a falcon on top representing Horus:

the serekh of Sekhemkhet

 

Horus is one of the gods connected to the afterlife. He is frequently seen as the god who presents the soul of the dead person to Osiris after the person has passed The Weighing of the Heart. Look carefully at a mummiform coffin and you might find a picture of Horus and Thoth pouring ankhs over the person who lays inside, or perhaps the two may be standing on either side of a large djed.

According to Egyptian mythology, Osiris (the father of Horus) was murdered by his jealous brother Set. Horus avenged his father's death by battling Set in a bloody war that represented the constant struggle of good and evil. Horus lost his eye in the fight, but it was magically restored by Hathor. The "Eye of Horus" is now a protective symbol of healing.

Eye of Horus