Everything, mostly….
Cuz this stuff is really hot.
Way hotter than melted cheese on a pizza. Way hotter than boiling oil in a deep fryer.

You need a few thousand degrees Fahrenheit or Celsius, either one, to make this happen (to be precise oxy-acetylene torches produce a flame that is 3480 degrees C or 6296 degrees F).
An oddly satisfying and at the same time mesmerizing experience, cutting through plate steel nearly an inch thick as if it were warm butter is nothing short of thrilling. The cutting torch starts by heating steel to it’s melting point. But the actual cut occurs when the steel ignites and is blown out the opposite side of the cut by high speed oxygen. You really have to try it to understand how much fun it is.

PP