Gemini belongs to the element of Air and moves through life in the Mutable mode, ruled by Mercury. Leo belongs to the element of Fire and moves in the Fixed mode, ruled by Sun.
Fire and air are natural allies — air fans fire, fire gives air direction. Together you think aloud, act boldly and rarely get bored. The balance to keep is between decisiveness and reflection.
The fixed partner holds the frame; the mutable partner fills it with colour. A balanced rhythm — but the fixed partner should try not to read the mutable partner's flexibility as indifference.
Both signs belong to the active, outward polarity, so your life together tends to be social, expressive and forward-moving. Give each other permission to pause sometimes.
What follows is a general read on this pair. Real compatibility depends on the whole natal chart — use the calculator linked on this page to compare two full charts when you're ready.