“Lead on, Macduff!” is a phrase often used to say “after you” when people are being polite and opening doors for someone, or showing that they will follow another person’s lead.
People who use this phrase think they are quoting Shakespeare’s ‘Macbeth’, but they’re not quite doing so: those are not the words Shakespeare wrote.
Both the phrase and its meaning have been changed over time.
What Shakespeare wrote was “Lay on, Macduff”, and Macbeth wasn’t opening any doors or following Macduff’s lead when he said it. Macbeth and Macduff were fighting one another, and only one of them would survive. The words “Lay on, Macduff” were Macbeth saying “come on, fight me!”
So, next time you open a door, or commit to following someone else’s lead, be careful about saying “Lead on, Macduff”. If they know their Shakespeare, they might just fight you!