Near Earth, Mg-water or Al-water rockets (a direct derivative) could propel Earth orbiting spacecraft. Mg and Al are high performance, "green" alternatives to hydrazine. Commercial and military satellites could use metal-water thrusters for on-orbit repositioning and orbit-raising. They could also be used in upper stages and as apogee engines. In a multi-mode propulsion system, a Mg-water rocket could provide high thrust while a Mg Hall thruster could provide low thrust at high Isp. This system would be both fuel efficient and responsive. Atmospheric applications of Mg-water combustion technology could include HALE aircraft. Naval applications include: a water breathing, high speed rocket propelled torpedo: a low speed , long range, unmanned undersea vehicles; long duration sensor power. Commercial, non-defense applications include very dense and green chemical hydrogen sources for fuel cell applications. This application may be of particular interest to the automobile industry. Mg-based rockets are attractive for Martian applications due the possibility of acquiring both oxidizer and fuel in-situ. Mg and Al could be extracted from the soil using electrolysis, while CO2 could be compressed from the atmosphere, and H20 could be obtained with a regolith reduction reactor. The initial targeted application is propulsion for a Martian PAV. Once in orbit, Mg based rockets or Hall thrusters could propel the samples to Earth. Mg combustion technology has other promising uses on Mars. A ramjet or turboprop could propel a Martian airplane. Mg and Al could also be processed, stored, and combusted to provide energy on demand. ARL's existing technology proves the feasibility of this option. Metal based rockets could also be used for lunar exploration. Al , Mg and O2 for oxidation can be extracted from lunar regolith.