When magnesium and iron react with steam, they produce

Less active metals like magnesium and iron reacts with steam to produce dihydrogen gas

$\mathrm{Mg}\left(\mathrm{s}\right)+2{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)\stackrel{\mathrm{\Delta }}{⟶}\mathrm{Mg}\left(\mathrm{OH}{)}_2\right(\mathrm{s})+{\mathrm{H}}_2(\mathrm{g})$

$2\mathrm{Fe}\left(\mathrm{s}\right)+3{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)\stackrel{\mathrm{\Delta }}{⟶}{\mathrm{Fe}}_2{\mathrm{O}}_3\left(\mathrm{s}\right)+3{\mathrm{H}}_2\left(\mathrm{g}\right)$