tip on welding sheet metal

Here's my tip on welding sheet metal: I am a beginner in welding. I try welding using an mma arc welding on sheet metal, but it always burn holes through. I tried all sorts of things but to no avail. I set to the amp lower and it either it sticks or it's not enough penetration.

My tip on welding sheet metal is to place an aluminum plate right below the metal you are welding so when you weld, the weld pool will not burn through.