What does Judges 6:20 mean?
Gideon has brought a large and generous meal to a stranger speaking as the Lord. That stranger, who apparently is the Lord God in some manifested form, has commanded Gideon to save Israel from the marauding Midianites (Judges 6:11–16). The only tool or instruction given was the promise of the Lord's presence as assurance that this can be done. Gideon has asked for a sign to verify this is truly the Lord (Judges 6:18).The Being waiting for Gideon is now called "the angel of God." He has been referred to as both "the angel of the LORD" and as "the LORD." That this Person is referred to as "the Lord" strongly suggests this is a Christophany: a pre-incarnate visit from God the Son, prior to His birth as Jesus Christ. He quickly tells Gideon what to do with the meal (Judges 6:19) he has brought: to put the meat and broth on a rock.
We're not told precisely what sign Gideon was expecting. What he sees, however, is more than enough to convince him that this Messenger is telling the truth. In typical fashion, even this confirmation will elicit fear and worry (Judges 6:22–23; Exodus 3:18–23).