I imagine that in a nearly Earth-sized ice planet with an atmosphere similar to that of earth, life has been able to proliferate. It first formed in the oceans below the ice, which are warm enough for life to survive. Then, after multicelular life emerged and the ice began to slowly get thinner (haven't thought why), life managed to get on land. The most alien thing about the life on this planet would be that, thanks to the ice and water's salinity, it is a very good electricity conductor. With the constant electric storms on the planet's surface, would life be able to survive and use this electricity after millions of years of adaptation?
I think this is possible, but not in the way many people think of it. Forget lightning for a minute, and think of solar storms. In 1859, Earth experienced the most powerful solar storm in history. Telegraph operators were getting shocks from their relays, and sparks were arcing off the telegraph poles across the whole planet. It was called The Carrington Event. Most scientists today believe if we had another storm like this, our society would be devastated. Planes could not fly, all our communications would be damaged or at least be useless until the storm ended. Satellites would fail and fall from the sky.
(Carrington Event major spike recorded by the British Geological Survey, September 1, 1859)
But one of the most interesting things about this storm was the charged atmosphere. The whole planet was electrically charged. Some telegraph operators were actually able to disconnect the batteries from their terminals, and still send messages! Every electrical conductor on earth carried an electric charge.
So your atmosphere can do this same thing by making the clouds a huge Van-de-Graaf generator. While the air is electrified (all the time), your animals are using the voltage across their bodies to metabolize their food, charge their biological batteries (modified muscle cells called electrocytes) with electricity in the air.
I feel you can not take this charge away however; your species will be dependant on an electrified air.
"Do you know what happens to a toad when it gets struck by lightning? The same as anything else."
So the biggest hurdle to this would be the adaptation part, when creatures that are struck by lightning are often not alive to reproduce.
Lightning delivers a lot of energy very fast, and each bolt can contain up to one billion volts of electricity. That will cook flesh pretty fast, so you have to first adapt them to be able to withstand that kind of power so they will be alive to reproduce.
I would start off before they emerge onto land. Like an electric eel these creatures use electricity for defense and to stun prey to eat. They are also pack hunters meaning they need to withstand the electric shocks of others of their kind. They begin to not only withstand the external electrical jolts, but to be energized by them. As the ice thins and liquid water is exposed, lightning strikes to the water happen more an more frequently.
Creatures that are near the surface, but not close enough to the strike to be overwhelmed experience these brief and very powerful bursts of electricity would get an extra surge of energy. Over time the ones that could withstand the more powerful bolts would be positively selected for. By the time the creature is able to fully transition to a land based existence they will have become fairly well adapted to lightning strikes.