Sun is the driving energy behind every living organism. It is one of the most important heavenly body considered in Astrology. As, Sun gives light and energy to all the planets and decide the luminous effects of other planets. Sun has a different effect on different sign of the Zodiac. hence, it depends on the horoscope from person to person depending upon the placement of Sun in it.
As Sun provides energy, it is up to the person to use the energy in positive or a negative way. The Sun sign also decides the rise of the person and its downfall also.
For a detailed insight of sun signs, you can visit their respective pages