The Mutable Signs are Gemini, Virgo, Sagittarius and Pisces. These signs are the least representative of their Elemental Natures. This is because the Mutable Quality is a sort of transition from Fixed to Cardinal, and they seem to behave in a way that is sometimes one and sometimes the other.
The Mutable signs are said to "distribute" the energy of the Fixed Signs, and "adapt" to the nature of the Cardinal Signs. You could say that the Cardinal Signs represent the urge to action, the Fixed group represents the need for stability, and the Mutable group expresses the necessity for change. All four Mutable signs bring the message of the need for variety and change to the other signs, each in their own way.
The Mutable Signs tend to take characteristics from the signs surrounding them; they tend to be more adaptable than the other two Qualities. Mutable signs also find it easy to deal with change, and tend to need lots of travel and activity. Because of the flexible nature of the Mutable Quality, they seldom commit to opinions, and consider "truth" relative, not absolute. They all are quick to turn a phrase, and can be quite gifted at anything requiring the use of words or the display of skills, but often have a hard time finding direction in life.
Gemini, being an Air Sign, is usually the most representative of the Mutable Quality. They tend to change their minds often, and usually have many interests that they don't mind talking about. Because the Air Element is always in motion, they become distracted easily, but they usually manage to find a way to put their imaginative and clever ways to good use. Being overly flexible in their opinions, they don't like to be pinned down into a commitment; the Mutable Quality explains why they become bored more easily than the other Air Signs.
Virgo is an Earth Sign, and is the most practical sign of the Mutable Quadrature. Their reasonable nature and practicality can descend to criticism, but that's because of the protective nature of the Earth Element, which drives them to try and help others. Like all Mutable Signs, they tend to be great conversationalists and good listeners, but the Earth Element may cause them to make unwise commitments, or to take too long to capitalize on opportunities. The Earth Element gives them reliability, but Virgos need more variety in their lives to satisfy the Mutable Quality.
Sagittarius belongs to the impulsive Fire Signs, and is certainly the most adventurous of the Mutable Signs. They often find it hard to stay in one place for long, and have more of a problem with anyone who tries to limit their freedom than any other Sign in the Mutable group. Sagittarians typically have difficulty making or keeping commitments due to their tendency to follow their impulses, but will come quickly to the aid of those whom they care about - both of these traits are a blending of the Fire Element and the Mutable Quality.
Pisces is a Water Sign and is the most emotional member of the Mutable Quadrature. They are very flexible in their opinions, and value their freedom as much as any other Mutable Sign. Being of the Water Element, they tend to be very volatile emotionally, and usually need to be around people they can depend on. Pisces people have an amazing ability to shrug off disappointment or emotional hurts, unlike the other Water Signs, because of the adaptability they get from Mutable Quality. They are likely to follow their feelings when they should not.
The Elements represent the ethereal components or substance of the Zodiac signs, while the Qualities speak of how the elements act; it's impossible to consider the Qualities alone as a factor in compatibility. The strong need for variety evidenced by people born in Mutable Signs may explain why they have difficulty with those who are too demanding or set in their ways. For instance, the adventure-seeking Sagittarius may find it difficult to deal with the security-seeking Cardinal Sign Cancer or the practical and materialistic people born under the Fixed Sign Taurus. The curious and expressive Gemini usually finds the Fixed Sign Scorpio far too serious.
Certain compatibilities exist between signs of the same Quality that are stronger than the Elemental differences. As an example, Virgo and Sagittarius share the Mutable Sign's love of travel, and Gemini and Pisces both love conversation and stories, and neither minds embellishing them. Despite the elements being out of balance, these signs get along well; the Aspects of the Signs tell us why.
Use this link to learn more about the Mutable Quality.