Earthbending

General information
Earthbenders have the best defence of all the other elements, while their speed is lower.

Metalbending
Metalbending is one of the balanced sub skills. It can be used for offensive attacks, as well as defensive. It can be unlock after level 70.

Seismic sense
Seismic sense is an useful skill, that can be used even if you're not facing your opponents. It can be unlocked after level 70.