An article “Magnesium can be burned at power generation plants” explains that the reaction between magnesium and water generates heat and the hydrogen generated from the reaction can be burned to produce high-temperature, high-pressure steam.
The following movie shows an experiment of magnesium engine at Tokyo Institute of Technology in 2006.
When 2mm-granular magnesium is mixed with water, it becomes muddy fuel. We can throw the fuel into an engine continually and burn it easily.
