Egyptian mythology is heavy on animal imagery, so much so that the zoomorphic gods of Egyptian myth are commonly recognized even by people who have never heard of their names outside a Brendan Fraser movie. Each animal has distinct iconographic and symbolic value to the ancient Egyptian religion far beyond just neat feathers or scary teeth, and one of the most common symbolic animals populating the heiroglyph-riddled walls of ancient tombs and monuments is the majestic lion.
Lions appear all over Egyptian art and religion; they are shown as conquering lords of the wilderness and dangerous guardians of important beings or places, showing off fearsome claws and teeth or simply existing serenely with all the implied ferocity at their disposal. Various deities appear with the attributes of lions, or even fully realized as divine lions themselves, and myths of those gods with leonine natures include their terrifying and powerful rampages and exploits in both good (protective) and bad (destructive) dimensions.
At first glance, it seems strange that lions are so common in Egyptian mythology, because lions, as a generality, don't live in Egypt. Not in the modern day, anyway; they were long ago pushed out of Egypt's habitable areas by the expansion of human civilization, not to mention hunting for both purposes of survival and for the prestige of overcoming such a dangerous creature. But during the ancient periods of Egypt's religion, when the gods were rising to power and the Pharaohs ruling in their rising and falling dynasties, lions did roam the Egyptian wilderness, usually at the edges of the deserts but often as close to the habitations of humanity as the Nile itself. They were seen as the terrible lords of the places where nature ruled supreme and humans must tread carefully, and successfully hunting a lion - a feat when the weapons of the time were bows, spears and hand-to-hand blades - was an accomplishment that could win a person great respect and even reward from their people.
In fact, lions in ancient Egyptian culture and myth are even more impressive when you realize that they were most likely members of the now-extinct Barbary Lion species, huge monstrous felines that could reach over ten feet in length at their largest.
Because lions were such impressive creatures and had so much obvious strength and power at their disposal, they became symbols of the rulers of Egypt as protectors of the Pharaoh and warriors of the kingdsoms; and those qualities were also imparted to the many gods and divine lions of Egyptian religion.
There are tons of lion deities on ancient Egypt's roster of deities, some of them among the pantheon's most famous members and others obscure except to dedicated Egyptologists. One of the oldest is Aker, the guardian lion (or lions, as the god often appears in dual aspect) who stands at the crossroads of the worlds of the living and dead and protects all horizons from the dangers of darkness and death.
Lions often lived on the edges of civilization or around the border between the lush lands of humanity and the desert wastelands around them, and Aker therefore represents the lion's symbolic role as the guardian of the border - all kinds of borders, physical and magical. Ruty, another form of the twin guardian lions, also appears especially often with the Egyptian gods associated with the horizon - Shu, lord of air, Geb, god of the earth, and Ra, the great king of the solar disk that rises between the two.
Probably the most famous lion god of Egypt is Sekhmet, the Lady of Slaughter, the ravenous and dangerous goddess of plague and warfare who acts as the right arm of Ra and the embodiment of his divine retribution.
Sekhmet is one of a procession of goddesses who function as the Eye of Ra, the lioness daughters of the sun god who defend him from danger and act as his military might when enemies must be defeated or mortals punished for any impious infractions. This setup mirrors the idea of the lion as a royal symbol of the Pharaoh and the representation of his power, but interestingly, the Eye of Ra (especially Sekhmet) is especially famous for, in various myths, deciding to no longer do the bidding of her ruler and to begin rampaging unchecked across the landscape or escaping to race uncontrolled across the wilderness. Even when the lion goddess is harnessed to be the strength of the ruler, whether Ra or the Pharaoh, she cannot truly be entirely controlled; lions are a primal power that always eventually breaks free.
Sekhmet is the most famous of the leonine eyes of Ra, but she isn't the only one. Her sister deity, Bastet, is far more well-known as the patron goddess of domesticated cats, but in her earliest forms she too was a lioness, and she also fought Ra's battles and eventually slipped his control, appearing as the lioness guardian of the Upper Kingdom as opposed to Sekhmet as the watcher of the Lower Kingdom. Her iconography gradually changed as she became associated more with gentle motherhood and the light of the moon rather than the warlike concepts of combat and the fierce heat of the sun, until she became the cat goddess that we all know and love now. And there were many other lionesses who went forth as Ra's powerful Eye, each one born of the sun god to defend him and eventually breaking away to indulge their own wild natures and violent powers - Mekhit, the free-roaming wife of the warlike Anhur; Menhit, the huntress of the fiery arrows; Mestjet, the lady of the dawn; Pakhet, the bringer of nighttime terrors; Shesmetet, the lady of the Pharaoh's regalia; and Tefnut, the goddess of the first moisture who escaped her family to roam the wilds alone.
Lion deities are usually females in Egyptian myth, which is not surprising, considering that lionesses are usually the hunters who seek and kill their prey on behalf of the less active males, but there are a few masculine lion dieties as well. Maahes is the most famous of these, the son of either Bastet or Sekhmet and the fierce protector of Ra on the solar barque Mesektet, where he stands side by side with Horus and Set to fight off the evil serpent Apep and prevent it from swallowing the sun god.
Modern-day Egypt has no lions outside of zoos and private owners, but their presence, in all its dangerous leonine glory, in its distant past is remembered and celebrated over and over in the myths of Egyptian mythology. On the Hero's Journey, watch out for teeth in the wilderness nights!