Quick Start

To create a simple MahApps.Metro Application with a MetroWindow do this...

<Application x:Class="WpfApplication.App"
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             StartupUri="MainWindow.xaml">
  <Application.Resources>
    <ResourceDictionary>
      <ResourceDictionary.MergedDictionaries>
        <ResourceDictionary Source="pack://application:,,,/MahApps.Metro;component/Styles/Controls.xaml" />
        <ResourceDictionary Source="pack://application:,,,/MahApps.Metro;component/Styles/Fonts.xaml" />
        <ResourceDictionary Source="pack://application:,,,/MahApps.Metro;component/Styles/Colors.xaml" />
        <ResourceDictionary Source="pack://application:,,,/MahApps.Metro;component/Styles/Accents/Blue.xaml" />
        <ResourceDictionary Source="pack://application:,,,/MahApps.Metro;component/Styles/Accents/BaseLight.xaml" />
      </ResourceDictionary.MergedDictionaries>
    </ResourceDictionary>
  </Application.Resources>
</Application>

<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="http://metro.mahapps.com/winfx/xaml/controls"
                      Title="MainWindow"
                      Height="600"
                      Width="800">
  <Grid>

    <!-- your content -->

  </Grid>
</controls:MetroWindow>

namespace WpfApplication
{
  public partial class MainWindow : MetroWindow
  {
    public MainWindow()
    {
      InitializeComponent();
    }
  }
}

There is also a Quick Start Guide on mahapps.com available.