One is ranged (lightning), the other is melee. Hold and attack wouldn't be a bad command.
You could also try getting a staff of storms or Tempest for your commander, to tap into their storm bonus. And remember that they can fly during storms.
Units with a ranged attack will use the attack when told to hold. After they are done holding, they will close to melee (and since storm demons are fliers, that's instantaneous).
One odd and fun thing about storm demons is that their ranged lightning attack works underwater which in effect makes them artillery without compare down there.