Leo is the height of summer, fixed and fire. The season is at full strength and not going anywhere, which is the structural meaning of a fixed sign.
The Sun rules it, which makes Leo the only sign whose ruler is the light itself. Everything traditionally attributed to it — display, warmth, the need for an audience — is a description of the Sun's role rather than a personality sketch.
This is also where the Sun moves most slowly through the zodiac, around 0.953° a day, because the Earth passes aphelion in early July.
Traditionally attributed
Warmth, display, generosity, and a need to be seen giving it.
Listed because it is what the tradition says, not because this site can check it. Everything above this line is geometry; everything in it is convention.