The signs or Rashis connected directly with the Fire element are Aries (Mesha), Leo (Simha) and Sagittarius (Danhu). Their ruling planet is Mars. Other planets of importance are Jupiter and the Sun (which is not a planet, but obviously a sun).

The upright triangle represents the Element of Fire.
(source: https://upload.wikimedia.org/)

You can say that the proportions of the elements of each Rashi are defined by the placements of the planets in the houses. A person’s temper is determined by how balanced the elements are in the horoscope. Most often people have an emphasis on two elements and lack the other two. The characteristics of a person in the sign of the element of Fire are the following: outgoing, bold, fierce, impulsive, inspirational, joyous, very active, very driven, spontaneous, intuitive, optimistic, passionate, quick in thought processes. The filtering of their mental impressions tends to happen in their digestive system. Meaning they are strongly connected with their digestion, being able to see this process as an expression of their emotional life.

The Fire element represents the personal drive to accomplish things.
(source: https://www.biddytarot.com)

Fire-Signs are driven by leadership. They have a drive to “become someone”. When there is an excessive emphasis on the Fire-element they can be described as egoistic, fanatic and overconfident. Uncontrolled Fire is destructive for others as well as for oneself. These people can suffer from burnout due to too many projects. They can go for their passions, never finish things and spill their energy. When there is a deficiency in the Fire-element people can be described as: cold, lack of passion, dull eyes, low resistance to infections, lack of energy or creativity. Fire-signs carry a strong energy that can be felt around them.

Aries or Mesha is a cardinal Fire Rashi. This person is highly committed to his or her work. Leo or Simha is a fixed Fire Rashi. This person is respected and recognized by others as well as admired and envied. Sagittarius or Danhu is a mutable Fire Rashi. This person follows his or her heart an intuition. He or she tends to be inconsistent and always reinvents him- or herself.