Mercury in Leo:
When Mercury in Leo people speak, they do it with authority. Some of them come across as know-it-alls, but the more mature ones speak with style. They want others to know about their presence of mind and their know-how.
Mercury in Leo men and women are adept at seeing the big picture, sometimes at the cost of ignoring the details. They are generally skilled at the art of persuasion. While others may try to win people over with logic, guilt, or wit, Mercury in Leo does it with warmth and good will. They are excellent at promoting ideas and getting their message across.
These people can be very attached to their opinions, taking pride in their beliefs, which are often rather idealistic. They are capable people on an intellectual level, and have an especial desire for self-expression.
Creativity is especially important to Mercury in Leo people. They present themselves with a certain amount of flair, and even drama. Often passionate and enthusiastic speakers, Mercury in Leo people get their message across with zeal. Some people with this position have developed a perhaps more sophisticated manner in which they present their ideas and thoughts, and these natives possess admirable style and warmth.
Depending on the confidence level of the whole individual with this placement of Mercury, a stubbornness in the face of criticism or over-sensitivity to anything less than praise is present. Whatever the reaction, Mercury in Leo natives can be mentally arrogant. Mercury, by nature, is detached and reasonable. In Leo, however, the ego comes into play very strongly when it comes to intellectual analysis.
With intellect and ego so closely tied, the ability to separate fact from fiction can be impaired. In some, boasting may be a problem. Probably the best way to handle this position is to find self-expression in some creative field. Mercury in Leo natives can be magnificent story-tellers, for example, mainly because they have such a wonderful sense of drama. They speak and write with heart. (Source).