guarantee? uummmm bet you're eating that word now huh? XD

Here is my theory. Amon talks about how his parents were killed and his face burned. He is actually a firebender as a child he was unable to control it killed his parents and hurt himself (I also think he killed Mako's parents, brothers maybe? idk) and then he was so scared of his own power he vowed to never bend again which explains why he was able to enter the spirit world and learn a type of energy bending.

maybe he met a lion turtle

If she's already bending more than one element than she's the Avatar.
There can only be one.

i never knew that two family members could bend different elements or that metal and electricity can be bent.. they could be changing things around in this series

Towards the bending two different elements in a family thing: Azula could bend electricity and Zuko couldn't. and Toph invented metal bending when she was captured by the guys her parents hired to bring her back home

The only issue in your statement is that, canonically, electricitybending is considered a specialized subset of firebending, much like metalbending is a subset of earthbending, or bloodbending is a subset of waterbending. This means that, if they trained hard enough / understood how / had the right mentality for it (I think it took rage, or something), all firebenders could lightningbend. Likewise, all earthbenders can metalbend, if they learn how, hence why there is such a large amount of them, in the new series. The police force is just a bunch of specialized earthbenders.

lightning is emotionless firebending. it is created by seperating your chakra and then redirecting the energy that is created when they crash back together. i'm not sure if only special earthbenders can metalbend or if it just takes a ton of training.

But what if the cycle is broken

But what if the cycle is broken

but it hasnt...