A message dialog asks a question or states a fact and waits for a button. It is drawn inside the MetroWindow rather than in a window of its own, so it dims what is behind it instead of stacking another frame on the desktop.

An input dialog asks for one line of text. Like the other dialogs it is drawn inside the MetroWindow rather than in a window of its own.

A login dialog asks for a username and a password. Like the other dialogs it is drawn inside the MetroWindow rather than in a window of its own.

A progress dialog reports how far a long-running operation has got. Like the other dialogs it is drawn inside the MetroWindow rather than in a window of its own.

The dialogs are shown by a MetroWindow, but a view model has no business knowing about windows. IDialogCoordinator bridges that: the view model asks the coordinator for a dialog and passes itself along as the context, and the coordinator works out which window that context belongs to.

When none of the built-in dialogs fits, CustomDialog gives you the same overlay with whatever content you put in it. It is a ContentControl, so anything that goes in a UserControl goes in a dialog.

MetroDialogSettings is the one object every built-in dialog takes. It is the last argument of each Show...Async method, and it decides the button labels, the colours, the font sizes, the animations and how the dialog can be cancelled.