Because I have so much to do and because this subject is well-known, and the Wikipedia page well written, rather than re-invent the wheel I'm quoting here from Wikipedia's "Planets in astrology". When I have more time I'll fill in the corresponding archetypes and equivalences with other symbolic and psycho-c\socio-spiritual systems of thought.
The Sun is the planetary ruler of Leo and is exalted in Aries. In Greek and Roman mythology the sun is represented by Apollo, the god of light. The Sun is the star at the center of our solar system, around which the Earth and other planets revolve, and which provides us with heat and light. The portion of the sky (or arc) that the sun travels in every year, rising and setting in a slightly different place each day, is therefore in reality a reflection of the Earth's own orbit around the Sun. This arc is larger the farther north or south from the equator the latitude is, giving a more extreme difference in day and night and in the seasons during the year. The sun travels through the twelve signs of the zodiac on its annual journey, spending about a month in each. The Sun's position on a person's birthday therefore determines what is usually called his or her 'star' sign; this makes sense because the sun itself is a star.
Astrologically the sun is usually thought to represent the conscious ego, the self and its expression, personal power, pride and authority; leadership qualities; and the principles of creativity, spontaneity, health and vitality; the life force. The sun also involves creative enterprises that are a projection of the person, from art and business to having children and parenthood (especially fatherhood). It also rules the fun side of life from sport and recreation to holidays and social events. In short, any occasion that 'allows us to shine'. The first-century poet Marcus Manilius in his epic, 8000-verse poem, Astronomica, described the Sun, or Sol, as benign and favorable. In medicine the sun is associated with the heart, circulatory system and the thymus. It was considered benignly hot and dry in nature, co-ruled the choleric humor, and symbolized the vital spirits. In modern astrology, the sun is the ruler of the 5th house. In the tradition, the sun ruled the 4th and 11th houses - the 4th house of the father/paternal ancestry and the 11th house of goals; it had 'joy' in the 9th house of philosophy and travel.
The Sun is associated with Sunday. Dante Alighieri associated the Sun with the liberal art of music. In Chinese astrology the Sun represents Yang, the active, assertive masculine life principle. In Indian astrology, the Sun is called Surya and represents the soul, kingship, highly placed persons, father.
Comments: to be added...