After rewatching Legends of Metru Nui, I discovered something interesting. The Toa Metru's personalities correspond to common teenage stereotypes, and many of their masks reflect that. Here's the list I've compiled.
Nokama: Nerdy girl. Her Mask's eyes could represent glasses.
Matau: Hotshot speed demon. hits on the nerdy girl. the long swept back mask could represent slicked back hair.
Whenua: History buff. Not sure if his mask ties into that or not.
Onewa: Bully. His Mask's one eyehole is reminiscent of sunglasses
Nuju: Genius. his telescopic eye is like a lab microscope
Vakama: Guy who's unsure of his place in the world. kinda depressed. His Mask has a mustache at the bottom.
So, what do you think? Am I seeing patterns that aren't there? Or have I uncovered a secret that has lain hidden for a decade?