Metals are unconventional hydrogen production materials which are of high energy densities. This paper comprehensively reviewed and digested the latest researches of the metal-based direct hydrogen generation and the unconventional energy utilization ways thus enabled. According to the metal activities, the reaction conditions of metals were generalized into three categories. The first ones refer to those which would violently react with water at ambient temperature. The second ones start to react with water after certain pretreatments. The third ones can only react with steam under somewhat harsh conditions. To interpret the metal-water reaction mechanisms at the molecular scale, the molecule dynamics simulation and computational quantum chemistry were introduced as representative theoretical analytical tools. Besides, the state-of-the-art of the metal-water reaction was presented with several ordinary metals as illustration examples, including the material treatment technologies and the evaluations of hydrogen evolution performances. Moreover, the energy capacities of various metals were summarized, and the application potentials of the metal-based direct hydrogen production approach were explored. Furthermore, the challenges lying behind this unconventional hydrogen generation method and energy strategy were raised, which outlined promising directions worth of further endeavors. Overall, active metals like Na and K are appropriate for rapid hydrogen production occasions. Of these metals discussed, Al, Mg and their alloys offer the most promising hydrogen generation route for clean and efficient propulsion and real-time power source. In the long run, there exists plenty of space for developing future energy technology along this direction.