rolling
Rolling is like a pasta machine for metal: you squeeze a thick slab between two rotating rollers set slightly closer than the slab is thick, and it comes out thinner and longer. Do it again and again through tighter gaps and a heavy ingot becomes a thin sheet, a plate, a rail, or a beam. It is by far the highest-tonnage metalworking process on Earth, because almost every flat product, from car body panels to soda cans to structural steel, starts as rolled stock.
The rolls grip the metal by friction and drag it through, and the reduction in each pass is limited by how much the rolls can bite. Rolling is usually done in two stages. Hot rolling comes first: the metal is heated so it flows easily, breaking down the cast structure into refined grains and doing the big thickness reductions cheaply, at the cost of a scaly, imprecise surface. Cold rolling finishes the job below the recrystallization temperature to get a smooth surface, tight thickness tolerance, and extra strength from work hardening.
The subtle honest point is texture. Squeezing grains flat and long tends to line up their crystal orientations in a preferred direction, so rolled sheet is anisotropic: its strength and its stretchiness differ along, across, and at 45 degrees to the rolling direction. This shows up as earing (a wavy rim) when you deep-draw a can from rolled sheet. So rolling not only sets thickness but stamps a directional fingerprint on the sheet's properties.
Steel sheet for a car door starts as a hot-rolled coil that is broken down from a slab, then cold-rolled to final thickness; the cold rolling adds strength by work hardening and gives the smooth, tight-tolerance surface needed for painting.
Hot rolling refines the grains and does the heavy reduction; cold rolling adds strength and finish, and leaves a directional texture.
Rolled sheet is not the same in every direction: the rolling texture makes strength and formability depend on orientation, which is why deep-drawn cups can develop wavy ears.