Use a pair of snips if you want to avoid power tools altogether and are working with thinner more flexible metal or need to make curved cuts.
How to cut corrugated metal roofing with circular saw.
Not only is it already meant to be stable and perfect for use with power tools but it goes perfectly with a cutting circular saw if you prefer to use that kind of tool over power shears.
Milwaukee 6370 21 13 amp 8 inch metal cutting circular saw this milwaukee circular saw tool is designed especially for metal cutting.
There are several ways to cut corrugated metal.
By far the best cutting surface is a workbench.