What material is the sword made of? Make sure to use an appropriate base coat and primer.
Insulation foam will melt if you spray it with spray paint. You can seal it with mod podge, gesso, watered-down elmer's glue. Plasti-Dip can work, but will obscure fine details.
It's very difficult to get a chrome or metallic look from a single spray can. For a good-looking paint job, you have to build up layers of color.
Instead, after your sealer/primer, do a base coat of flat matte black - I prefer the 99-cent Project Source brand from Lowe's, as a base coat it's surprisingly great for the price. Then, build up the metallic look by VERY LIGHTLY misting on and dry-brushing on metallic silver. There are a variety of ways to do this. Rub-n-buff has a great reputation but I haven't used it. I usually use metallic Platinum from a spray can, misted in the general direction of the prop from a good distance; silver sprayed into a rag then wiped onto the prop; or, acrylic paints and paintbrushes by hand.
I'm going by these reference images for coloring - it's NOT just shiny polished/chrome metal.
Look at the blaster in these posts for an example of what I'm talking about. This is still pretty dark gray, but if you want it more silver, you can build up more and more layers of silver on top of the base black coat.
Black base coat:
Silver from a spray can, a VERY VERY light coat to lift the black, then some more wiped from a rag onto the blaster:
Final (bottom right):