The notion that Jesus was speaking metaphorically when he told the apostles to arm themselves with swords is refuted by common sense --- including yours --- and by most Christian interpretation of Scripture.  Nothing in that passage argues for the aggressive use of swords.  That's obvious.  But given what's equally obvious --- that the apostles would soon be in great danger --- Jesus meant to tell them it was permissible to arm themselves in self-defense.  That, indeed, is the common-sense and commonly accepted interpretation of the passage.