Sir Sean Connery and Christopher Lambert got along so well during filming that they called each other by their characters' names even when they were not filming, and it was at Lambert's insistence that Connery and his character returned for Highlander, le retour (1991).
All of Sir Sean Connery's scenes had to be filmed in a week, due to Connery's schedule. He had a bet with director Russell Mulcahy that they would not finish in seven days, but Mulcahy won the bet. Connery earned $1 million for his week's work.
The swords sparking while clashing was accomplished by attaching a wire to each sword that led down the arms of the actors to a car battery. One was connected to the positive terminal and the other to the negative terminal, so when the swords touched, there was an arc.
While filming the scene at Eilean Donan castle, the car park by the castle had to be covered up with tons of peat to disguise it. The house located by the bridge out to the Castle was boxed in with hardboard and painted over, so that it looked just like real stone even when you stood right beside it. Extras were paid £25 a day, with a ten pound bonus if they took their own horses. A lot of the locals took several days off work to do it.
Queen originally intended to record only one song for this movie, but after viewing footage from the movie, they were inspired to write more. The band members each had a favorite scene and composed songs specifically for them. Brian May wrote "Who Wants to Live Forever" during the cab ride home after seeing the movie, and Roger Taylor used the line "It's a kind of magic" as the basis for the end title song.