MahApps.Metro use
Download MahApps.Metro
PM> Install-Package MahApps.Metro
Add in MainWindow.xaml
xmlns:Controls="clr-namespace:MahApps.Metro.Controls;assembly=MahApps.Metro"
Then replace the Window label with the following label
<Controls:MetroWindow x:Class="WpfApplication.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:Controls="clr-namespace:MahApps.Metro.Controls;assembly=MahApps.Metro"
Title="MainWindow"
Height="600"
Width="800">
</Controls:MetroWindow>
MainWin