1) There is actually a difference between figurative speech and idioms - that is, idioms are fairly well-known. I wouldn't count any of these as idioms. However, one common idiom in the same vein is "I'd take a bullet for you." 2) Black and blue = bruised. "Beat me till I'm numb" = because you do it anyway, so I may as well tell you to do it. "Tell the devil I said hey when you get back to where you're from" - Send the devil my regards, as you're clearly going to Hell. In fact, you're such a terrible person that you probably came from there anyway. 3) Interpretation: "You are two-faced. You act nicely to me in person, but then you sabotage my life when I'm not there." (For example, by removing the brakes from his car, which would surely cause an accident.)

I'd catch a grenade for ya,i'd jump in front of a train for ya,i'd throw my hand on a blade for ya. Black & Blue- Here he is saying that the girl he is singing about has been assaulting him and that he is bruised. The only colloquial expression here that is commonly used would be 'Black & Blue'. For example: 'I was all black and blue yesterday after my rugby match'. This means that after my rugby match yesterday I was bruised from people tackling me.

so what does it mean when it say "beat me till im numb cause im writing figutive language on it what does that part mean?