Angels are bright still, though the brightest fell;
Though all things foul would wear the brows of grace,
Yet grace must still look so.
– William Shakespeare
Macbeth, Act 4, Scene 3. Malcolm isn’t yet ready to place his complete trust in Macduff. Macduff appears to be good, he concedes, but everything evil tries to wear the disguise of good. However, Malcolm says that looking good doesn’t mean you are evil, because good people also look good. The “brightest” is a metaphor for Lucifer, the once brightest angel who rebelled against God and became the Devil. Throughout this scene Malcolm test Macduff’s loyalty and intentions.