Alane is an aluminum metal hydride. Its chemical formula is AlH3. It's somewhat unstable and highly flammable.

It's used extensively in industry. It's currently being examined as a possible rocket fuel. Mixing small amounts of it to a hydrocarbon makes the fuel about 25% denser, but does not seem to affect the thrust per unit mass (ISP) much. Thus the tanks on the rocket can be made smaller, and lighter for the same overall performance.