Upright
Authority and societal order. Balance, security, and conventional values.
4. The Emperor
Authority.
Reversed
Excessive force, or the need for the assertive qualities of The Emperor.
Element: Fire
If The Empress is the mother of the Major Arcana, the Emperor is the father. As you might expect, some tropes of the Tarot are very outdated. The Empress is defined by fertility, and The Emperor is defined by authority. It represents societal order and the enforcement of that order. It brings a sense of balance, security, and conventional values. It is about the power of society and its laws, and the enforcement of those laws.
The Emperor may represent someone who is authoritative and in a position of control. It may represent larger themes of conventional society or enforcement of societal order. Or, it may mean someone is a bringer of that order in some capacity, someone who tries to organize and balance otherwise chaotic environments. It can also mean patriarchy in general, either in a small scale in homes and communities or at a larger scale in society.
When reversed, the Emperor takes on negative qualities. Excessive force, with a concentration on discipline. It may also indicate a situation where things have gotten loose and chaotic, and the assertive style of the Emperor is needed to right the situation.