Here is the honest part first: Aries and Leo will fight about who is actually in charge, and neither will enjoy losing that fight. Aries moves first, decides fast, wants to book the flights tonight. Leo wants that same decision made with a bit of ceremony, some acknowledgment that their input mattered, maybe even a little applause for the idea. When Aries just charges ahead and makes the call solo, Leo does not feel efficient, they feel skipped over. That sting lands harder than Aries expects, because Leo's warmth comes with a real need to be seen and consulted, not just included as an afterthought.
Underneath that friction, though, is a lot of genuine heat that works in this pair's favor. Both are fire signs, so there is no translation problem when it comes to enthusiasm, spontaneity, or wanting a big life rather than a careful one. Aries brings the spark that gets things moving, Leo brings the staying power and the flair that makes it feel like an event rather than an errand. Mars gives Aries its directness, the Sun gives Leo its steady radiance, and together they can turn a random Tuesday into something that feels worth telling people about.
The real work is Aries learning to hand Leo the mic sometimes, even when it slows things down, and Leo learning that Aries's abruptness is impatience, not disrespect. Get that right and this becomes a couple who argue loudly, forgive quickly, and generally have more fun than anyone else in the room.