It's been a long time when I last developed a Windows Form Application but today I am doing it again.
The thing what I see is that Win Form still uses those old style UI tools like buttons etc. However Microsoft and Windows have changed their design language quite a bit to flat Metro/Modern UI.
Is there a way to make use to newly style tools for Windows Form Applications? Preferably without using any 3rd party plugin?
I am working with .Net 4.5, On Windows 8.1 with VS 2012.
You have two ways to do this.
If you want to stick on with Win Form Applications, then just change the buttons and controls to flat style in properties and for button, place flat Metro style icons images that suit your application. I am currently doing that to give a new look to my existing application.
As said in the comment, if you are ready to design a whole new application, the WPF is the best choice. If you are targeting the Windows Store, then make use of Blend for Visual Studio 2012. It will assist you in creating professional Windows 8 Applications.