The Fire element is one of spontaneity, inspiration, intuition and big passions. Fiery guys and gals are excitable, impulsive and love to light a fire under others.
The Fire signs are Aries, Leo and Sagittarius.
The signs of the Zodiac are grouped in four triplicities based on their element. The other triplicities are water signs (Cancer, Scorpio, Pisces), air signs (Libra, Aquarius, Gemini) and earth signs (Capricorn, Taurus, Virgo).
My favorite phrase for fire signs is Spirit in Motion.*
Those with planets in fire signs have a simmering at-the-ready stance, as they hunt for things that light them up. They're prone to sudden illuminating flashes of insight and bursts of enthusiasm. Like fire itself, they can flare up when inspired, making them seem very passionate about life. They like to live large, and often feel frustrated by mundane chores and duties.
Fire signs are known to be intuitive, and to rely on gut-level instincts. Going on faith in their inner guidance gets them far, but they have a tendency to skip crucial steps, or to be unaware of the emotional impact of their actions.
Along with the triplicities, there is another grouping in astrology, known as the qualities. These are Cardinal, Fixed and Mutable -- each element has a sign with one of the qualities. Among the fire signs, Aries is cardinal, Leo is fixed and Sagittarius is mutable.
Fire and Water
Fire's greatest gift is being able to inspire, and this appeals to Water's desire for meaning. A generous Fire person shows Water how to be in the moment, even if they're carrying lots of psychological baggage. Water takes Fire on an emotional journey that helps them see how they're related to others. At its worst and most out of balance, Fire can zap Water by being totally overwhelming and Water smothers Fire when it offers only insular, claustrophobic intimacy.
Fire and Earth
Sometimes Fire has lots of visionary ideas that Earth can help put into tangible form. This can make pragmatic Earth feel needed and appreciated, not to mention that Fire's enthusiasm is contagious. If Earth becomes too slow and plodding for Fire, this match could get snagged in frustration. Through Earth's eyes, Fire may seem unrealistic and unwilling to do the legwork to make things happen.
Fire and Air
When Fire and Air get together, there can be a lot of inspired thinking. Fire helps Air find focus when scattered, and adds optimism to any plans hatched. Air can articulate the big picture for the impulse-driven Fire, while the latter keeps things from being all talk and no action. These two keep eachother in stitches, open the doors of perception and find new ways to astonish the other.
Fire and Fire
When Fire meets Fire, life can be an exuberant adventure. It's a vital match where there is mutual inspiration and encouragment. The challenge comes when fiery temperaments turn into struggles for dominance. If there is only drama, without an emotional foundation, this match can burn itself out.
When the fire element is present, there's a warm radiance, a trust in life's journey and a willingness to take risks. Any party or celebration is made better with the presence of a fully-charged up fire sign. They're great catalysts for play, and liable to unearth the spontaneous side of those around them. Because they sense a golden thread of destiny and potential running through their own lives, they have a knack for leading others to theirs.
Fire signs act on instinct or "sixth sense," and that makes them look reckless to more cautious types. They're actually following a powerful intuition that keeps them at the leading edge of fresh experiences.
Fire is infused with the divine spark, and this can spread like wildfire to everyone around them. They've got a lust for life that is enviable. Those that are weighted down might try to toss a wet blanket on their enthusiasm, so Fire must vigilantly guard its beacon. It's important for them to have cheerleaders to fan the flames of their interests.
But Fire that thinks only of itself learns the wisdom of the other elements the hard way. They'll keep coming up against resistance, until there is willingness to see there are no short cuts. Each of the other elements has something to offer, and in return, Fire gives off a glow that is as nourishing as the rays of the Sun.
*From Per Henrick Gullfoss' The Complete Book of Spiritual Astrology.