The visual behavior is the way the control appears when it is in a certain state.
Since we’re following semantic versioning, we promise to not break anything from version 1.0 to 2.0. Metro now allows to define custom themes for the application.
Metro follows Semantic Versioning, at least API wise.
Please note that minor visual changes can still occur if there’s a need for them.
A control that inherits from User Control is a control that can be quickly created, but it does not use a Control Template and you cannot customize its appearance.
When you define the visual structure and visual behavior in the Control Template of a control, application authors can change the visual structure and visual behavior of your control by creating a new Control Template instead of writing code.