App.xaml

<Application x:Class="FacebookCloneApp.App"
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             xmlns:local="clr-namespace:FacebookCloneApp"
             StartupUri="Login.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/Themes/Light.Steel.xaml" />
            </ResourceDictionary.MergedDictionaries>

            <Style x:Key="PageStyle"
                   BasedOn="{StaticResource MahApps.Styles.Page}"
                   TargetType="{x:Type Page}">
                <Setter Property="Background" Value="Transparent" />
                <Setter Property="Template">
                    <Setter.Value>
                        <ControlTemplate TargetType="{x:Type Page}">
                            <Grid Background="{TemplateBinding Background}">
                                <Grid.RowDefinitions>
                                    <RowDefinition Height="*" />
                                    <RowDefinition Height="Auto" />
                                </Grid.RowDefinitions>
                                <ContentPresenter Grid.Row="0" />
                                <TextBlock Grid.Row="1"
                                           Margin="4"
                                           FontSize="48"
                                           Text="{TemplateBinding Title}" />
                            </Grid>
                        </ControlTemplate>
                    </Setter.Value>
                </Setter>
            </Style>
        </ResourceDictionary>
    </Application.Resources>
</Application>