IE10 comes with Flash built-in though it's highly restrictive (you can remove the restrictions to a certain extent). Microsoft is pushing for the move away from Flash to HTML5 like Apple and Google.
I have yet to come across a flash site that didn't work on my Surface RT whether it be on Desktop IE or Metro IE. If you don't feel like modifying the file yourself someone has come out with a tool that you can run that will automate the process including clearing the browser cache.