I need to talk about this for a second.

This is right after Gandalf says, “A balrog. A demon of the ancient world.”

I just love how PJ chose to cut to Legolas’ face because he is exactly who you should cut to at this moment. You need an elf to show what it really means. Other than Gandalf, the rest of the Fellowship can sense something is gravely wrong, but they don’t understand just how grave. Like Gandalf, Legolas knows the terror. He understands the gravity of what lies around that corner. He’s got a piddly little bow and he is mere steps away from a demon of the ancient world. This frame shows a kid coming to the realisation that he is way out of his depth, that this mission will take him to places he only knew to exist in legends of the Elder Days, a time long gone, barely history. 

He’s probably one of the youngest elves in Middle Earth at this point. He probably grew up on stories of the balrogs, slaying the ancient High Kings of the Eldar and tearing Middle Earth apart, thousands and thousands of years ago. They are legends in old crumbling books, read illicitly by a little elfling who was kept up at night by the terrible tales.They are the monsters under the bed and the shadows in the heart of the forest. They are the beasts behind the winged hordes of hell, that older elves, who’ve seen the worst that Arda has to offer, always assured him were no more than distant nightmares, stories relegated to dust and ancient memory. Except now they are real. They are here. They are coming.

The best part is that in the books he just starts screaming when he lays eyes on it

In its right hand was a blade like a stabbing tongue of fire; in its left hand it held a whip of many thongs.

‘Ai! ai! wailed Legolas. “A Balrog! A Balrog has come!’

Legolas can be relied upon to have the correct reaction to everything.

It is not necessarily normal, or socially appropriate, or sane, but it is always 100% correct.