Li + H2O → LiOH + H2
The equation is currently unbalanced, so to balance it out, you have to have the same number of each molecule on each side. It'll look like this:
2Li + 2H2O → 2LiOH + H2
Also, in case you want to identify the phases as well, it'll be like this:
2Li (s) + 2H2O (l) → 2LiOH (aq) + H2 (g)
"s" is solid.
"l" is liquid.
"aq" is aquas.
"g" is gas.