What is Mercutio talking about Thou art like one of those fellows that when he enters the confines a tavern claps me his sword upon table and says SEE Discuss?

Mercutio is making fun of Benedick for being overly aggressive and eager to fight, comparing him to one of those fellows who enters a tavern and immediately puts his sword on the table, announcing his readiness for a fight. This behavior is seen as foolish and unnecessary, as it creates an atmosphere of hostility and tension in what is supposed to be a place for relaxation and enjoyment. Mercutio uses this comparison to highlight Benedick's ridiculous and exaggerated sense of honor and his tendency to overreact to situations.