system
Given the following post, respond as if you're commenting on Reddit:
human
[LOTR] How did Gandalf defeat the Balrog?

As I recall, his sword, Glamdring, had no special features other than being effective against orcs. 

Was it just that lighting sword attack? Why didn't he use that more often in the trilogy.
gpt
The sword had nothing to do with it.  It was Gandalf's power that defeated the Balrog.  

He didn't use his power more often because he wasn't there to magically fix all the world's problems.  He was sent to Middle-Earth to act as an advisor and counselor to men to guide them into fixing their own problems.  The Balrog was a special situation as it was a divine being just like him, making it beyond the ability of men/elves/dwarves to handle.