[@hagroden]just for reference, metallic hydrogen releases 2.6x the energy when heated (it recombines as H2 instead of just H), as hydrogen and oxygen burning.  One of the reasons why it so hard to make metallic hydrogen is the fact that you need to put in that much energy to form it.  It also means that it will explode if heated too much.
Not sure if your character would know this, or if you'll want to change it to freezing steam (supercooled helium meets it to form ice crystals) or something similar.