It's a variation of firebending and personally I don't really am keen on the idea that it gets elaborated on unless it would be for only a select few characters. One of the few things I didn't like so much in the first season of LoK, was the expanding on certain bending variations.
Ok metalbending I had no issues with as it was still limited to the metalbending police, it was a skill that truly had to be learned under the guidance of a teacher. There were no earthbenders shown I think that could bend metal outside the police. However I had several mixed feelings about lightning being so widespread. I already explained this a few times a year ago when LoK aired that within the flow of the series and Zuko's personality, it's explainable as why so many firebenders can use it now, still for something that was a generation ago an elite-skill, it seems it became a bit too easy to obtain. But what really bugged me was the bloodbending, which was a skill supposedly invented by Hama and after her only Katara was supposed to know it. Now they made it appear like it was some kind of KG without even an explanation as why some could use them all the time and others only during the full moon.
I personally hope that we finally get to see a variation of airbending.
Damn, I miss watching the Avatar. 
