The archwire is a wire that connects each brace. It does the actual work of aligning the braces, which will line up the teeth. It is made from highly resilient material that allows it to return to its original shape, after you have bent it. It is not like a paper clip that will stay bent.
The wires come in different sizes, shape and composition of materials. The size of the wire is measured by the thickness of the cross-section in thousands of an inch. A common round wire size is 0.016 inch, whereas a common rectangular wire is 0.017 by 0.025 inch. All of them are made from stainless steel materials. The various combinations of materials like chromium, cobalt, nickel, titanium and copper will greatly influence the bending properties of the wire.