The sun plays in an important role in many cultures. Several prominent early civilizations were involved in worshiping the Sun - such as the Romans, the Egyptians, the Aztecs and the Incas. While other cultures also paid homage to the sun, in these specific areas, the Sun was their highest god.
In Rome, the sun god was Apollo. He was thought to bring the sun each morning in a chariot across the sky. He also was considered to be the god of healing and arts.
In Egypt, the god Ra was in charge of the sun. Ancient Egyptians believed that Ra went through various transformations throughout the day, just as the sun did. He was the most important of all of the Egyptian gods, and pharohs from the fifth dynasty forward took the title "Son of Ra".
In Aztec culture, Huitzilopochtli was the god of sun and war. The patron deity of the Aztecs, it was said that he was supposed to guide the Aztecs to a promised land in the south. Human sacrifices were at one time made to this god in hopes of winning wars.
The rich mythology surrounding the sun means there is a wealth of different tattoo styles that can be found depicting its image. Many choose to get the sun and moon depicted together, as they are complimentary and, in some cultures, symbolize male and female power.
Others choose the blocky, tribal style of Aztec suns. The sun can also be a symbol of rebirth, so some people choose to combine it with other imagery such as Celtic Knots and Stars. The light and dark, good and evil symbolism are also a reason that people are so drawn to these tattoos.