Both have got egos to burn and both like to lead. Aggressive Aries wouldn't dream of taking second place, and kingly Leo needs constant admiration. Usually they can work it out by having Leo play the emperor and Aries play the general. The trick is for neither to take the other all that seriously.
It's a fine combustible sexual match, for both are fiery and romantic. Aries is optimistic and open to life, Leo is generous and good-hearted. If neither tries to deflate the other - and if they can find room to compromise about who dominates whom - this should be a happy mating.