All right, so my drawing skills for these aren't the best, and they're a little rushed, but just bear with me.
Now, it seems as if the idea of Kopaka being the Toa of Lightning is being set down, and while I don't entirely agree with that, I might as well go with the flow and offer some ideas for it.
The Region of Lightning in my concept art consists of several mountain ranges in a static-filled, ozone-heavy sky and environment. Up above, rainless clouds constantly sent forth bursts of lightning and energy, and to take advantage of this the villagers have built special mountaintop villages along the highest mountains.
Special rods built at the peak of these mountains, the highest points on the entire island itself, take the shock of these energy bolts and transfer them down the mountain-range through special towers that transmit the electricity. Built into the sides of these mountains are special, mechanical hubs and villages that take advantage of the electricity constantly surging through the mountains to power everything.
The electricity in question continues on downward through the mountain before hitting a Power Plant at the base of the mountain, where special batteries are charged. These batteries are then sent to the other villages to harvest the energy, and markets have been set up there to take advantage of the commerce there. Trolleys leading up to the higher villages have been set up at these Power Plant Markets.
The main, central village would be built atop the island's highest peak, named Mount Ihu after the brilliant inventor who discovered how to harness the power of lightning itself and use it to improve everyone's everyday lives.
The Lightning Rods transmit some of the energy from the peak to the barriers around the village, creating an electrified wall that keeps away Rahi, wild Rahkshi, and other threats. Even when time is shut down and the matoran freeze, lightning continues to rage, powering these villages and keeping enemies and Toa alike away, like an active ghost village.
However, other parts of the region are left vulnerable to threats, and soon wild Kurahk have begun to attack the Lightning Rods that transmit energy.
Kurahk are already hyper-active aggressive, but as a result of some feeding on the energy cables, they've become charged with Lightning and have become twice as dangerous. These Charged Kurahk have developed a taste for energy and are immune to Kopaka's attacks, hungrily absorbing them and launching off their own energy bolts. Thankfully, the seemingly-living defenses of the villages keep the Kurahk from entering and attacking the frozen Ko-Matoran.
After time is unfrozen, Kopaka quickly introduces his comrades to a popular sport in Ko-Koro, even more popular than the island-wide sport of Kolhii; Electric Surfing.
At least two riders start on special pods at the beginning of a massive grid made of railways and tracks. Along these complex tracks are special Lightning Rods that take in bursts of lightning that rain from the heavens above, charging the tracks they've aligned with and giving the rider on them an additional boost of speed. Special levers on the riders' pods allow them to switch tracks, and some will even circle back to where they started to catch an incoming powerful current of lightning surging through the grid.
Electric-Surfing has some basis in luck, but a skilled player can beat even the luckiest one by using their currents and turns wisely to get to the finishing line.
Electricity constantly surges through a massive roof above the Koro, giving light and surging to the city below through special pillars.
(This drawing isn't so good)
Lightning tends to flash through the mechanical village on a rhythmic or else chaotic basis. Due to the seemingly fickle nature of Melum, the Lightning Deity said to send these bursts of energy to the mountains, the Ko-Matoran have a culture valuing luck and daring acts. Many will wish a friend good luck by stating, "May Melum smile upon you with a flash of energy!" This luck-based culture has a side of gambling to it, and gives thrill to some Ko-Matoran as they anticipate Melum's grace.
Cables sometimes slither through these villages. The Power-Plants, some at the base of the mountains, others carved into the side, have special, almost rhythm-based security systems based on a current of electricity that runs through the building, sent down from the lightning above. Special switches can redistribute these currents, and only the most skilled Ko-Matoran Electricians can navigate this apparent puzzle of lightning to enter the workplace. Ko-Matoran, needless to say, pride themselves on this intellectually-based security system and boast it as the best on the island, with only the smartest deserving entry to the power-plants.
Legend also has of a special power-plant, more elaborate and maze-like than the rest, hidden in the core of a mountain, accessible only through a secret tunnel from the side. Some say a great treasure is within this plant... others claim it's the island's worst secret. Whatever it is, the Toa must brave the perilous energy and the fickle nature of Melum as they combat energy-draining Kurahk and other parasitic rahi as they traverse the rocky slopes.
They also must heed the massive rocks that float throughout the skies, stones with a special magnetic property that causes them to float through electro-magnetism when in the vicinity of so much lightning. These 'floating islands' are sometimes attached through special cables to the mountains, and are usually the sights of Electric Surfing grids, clubs, and other places.
I hope you guys liked the art and ideas I supplied for the Region of Lightning! Some of these drawings were a bit rushed, but I figured any visual aid is better than none at all!