A blind girl wearing hipster glasses...

i am feeling that Magneto is a little bit left out here

See the problem with that reaction image is the fact that Toph herself was the one who taught metal bending with her metal bending academy.
Besides that, in Legend of Korra only the police force can metal bend, so I'd hardly call it mainstream either.

We don't know that only police can bend metal, only that the only ones shown to do so are police. It's like lightning, before, it seemed like only Fire Nation royalty could do it. Now it's commercialized.

The lightning as a common power seems odd to me, given the difficulty required in learning and being able to use the technique.

MFW a bunch of firebenders using lightning out of nowhere.

That... or it isn't as difficult as it was made out to be, but like any skill, practice makes perfect? It's possible that it was a skill only for the Fire Nation royals, but it somehow spread out, maybe even by AZULA...

I think the point was that it requires tremendous skill and personal will power and balance to be able to use it properly. Hence why only a select few of the best are shown using it in ATLA.

I suppose it's possible that the more modern technique is a weaker version of the familiar old, though.

I don't think so. I think that it involves a tremendous concentration of heat at the fingers to create a spark, which is then fueled by the firebenders' "chi". I think it's more a matter of skill than power.

FOR THE RECORD: i always see when you comment because of your avatar, draws my attention, and then i have a FUCKTONNE of trouble pronouncing your name

For the record? It's "katana" but with the "na" sound after the second syllable, rhymes with the "ka" syllable.

I know!!! but i always say "Katana" "katanaka" "katanata" "ratatata" or some such nonsense

Would it help if I used my other handle, "kakatana", with just the extra "ka" at the beginning?

Not really complaining broski, it just messes with my head at first glance, i think it's brilliant!

Ive only seen a few episodes of Legend of Korra. Thwanks