i dont remember his exact words, but something the guru said led me to believe that people of other nations can also bend elements from another nation. i mean, it's not like someone has ever tried to bend an element from another nation have they? maybe since the nations are so divided ppl just get the notion that they can only bend the element that is "native to them". and no doubt the way each nation's society function's differntly, and how the ppl are conditioned also has to do with the mental aspects of bending. eh i dunno, i coulduve totally misinterpreted a little quibble from the guru...

No, I'm almost positive they can't. But they can apply another bending STYLE to their bending. Like Iroh does a waterbending move to re-direct lightning. He didn't water bend. It has also been stated that only the Avatar can master all four elements. That and the Guru's talk was mostly just a way to say Toph can metalbend. The writers just threw it in to make Toph great.

if that was true then what is the entire point of an avatar?

I wouldn't suprised. Toph saw the connection between earth and metal. But it wouldn't be interesting if everyone can bend all 4. Defeats the purpose of the Avatar. So I pick no.

I think that he meant it was possible to bend different,??more advanced??branches of an element ex.earth:metal or fire"lightning

Hmm, Good point man.

If one nation can bend what the other nations could bend, why would there be Avatar?
Why did we not encounter anyone who can bend two elements?
The answer obviously is no.
By the way, when the Guru said all the nations are the same, he meant that we are all made out of flesh and blood.
We're all humans.

I said yes, but i only meant that they can apply another elements style into there element.?? For example, the Dia Li can shoot rocks which is using air.?? Or when Katara lifted Aang and herself away with her waterbending when he died.?? She used propulsion which is a form of air bending.?? So no they cannot use another bending form but they can inject another bending style into there type of bending.

But, remember on the episode "The Blind Bandit", there was a Fire Nation person Earthbending. Mabe he was born or grew up in the Earth Kingdom, but I don't see how someone born in one nation has to bend that element of the nation they were born in, if thier family heritage was from another nation. But also, I just remembered, from the episode "The Swamp", there were waterbenders in the Earth Kingdom. So, I guess nations have nothing to do with what kind of benders live there.