One man's trash is another man's treasure, so scavenging discarded scrap materials is a great way to obtain resources you may need. This is especially true in urban locations, since junkyards and workshops are often loaded with excess bits of fabric, wood, rubber, PVC pipe, and metal that can be had for low cost or even no cost. These materials can be reworked by an industrious survivalist into tools, shelters, and other useful items.
Sheet metal is one plentiful material that's especially handy for building durable shelters, but it's not as easy to work with as wood, plastic, or fabric. The quickest way to break down sheet metal is with power tools, but those are heavy, expensive, and reliant on electricity. Tin snips are a useful hand tool that can do the job, but they're specialized enough that you may not have a pair when you need them. They're also not ideal for long perfectly-straight cuts. In a pinch, it's possible to precisely cut thin-gauge sheet metal using steel wire.
This old-school method to cut sheet metal requires a few feet of strong wire, such as baling wire or piano wire, and is most effective on thin and flexible metal, such as corrugated roofing or siding panels. The user's body weight is applied to hold the metal against the ground, and the wire is pulled upward to cleanly slice through the metal. The following video from YouTuber Phil Crockett shows one method:
Steve Garrison demonstrates another variation of this technique that uses a screw to retain the fixed end of the wire, and eliminates the wood 2x4s seen in the previous video:
If you ever find yourself with some sheet metal and no specialized tools, this manual cutting method may come in handy. You can probably even scavenge the wire you need in the same place you found the sheet metal.