Page

To style a Page you can set the Style property.

<Page x:Class="MetroDemo.Navigation.InterestingPage"
      xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
      xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
      Title="Interesting Page"
      Style="{DynamicResource MahApps.Styles.Page}">

    <StackPanel>
        <TextBlock>Sorry, nothing is here.</TextBlock>
    </StackPanel>
</Page>