The Sun signifies your sense of identity, self-image and will, and is the single most important planet in your birth chart. It is said that the Sun represents your life goal and destination, while your Moon is the path you are obligated to take because of your instinctive reactions. The Sun in your birth chart shows where your love interests and relationships get along, and a compatible life partner unlocks your life energy and the unfolding of your inner-self and creative ventures.
The Sun rules Leo, the natural sign of the fifth house associated with fun and romance, and this is where it loves to shine. It also is the house of children and the need to procreate, along with creating through procreation personal memories of one's own childhood. The Sun represents our conscious mind in Astrology, it is our personal ego and basic identity and overall vitality and life purpose.
In all cases of partnership, where we need to adjust our personality to another, the closer we are in accord and harmony, the more successful the relationship will be, and it has been found that one of the strongest affinities is when a female's Sun (representing the male) is the same as the male's Moon (representing the female). If Sun signs and Moons are incompatible, you can expect quarrels and disagreements to naturally occur.