Funny enough, if you read the guidelines for Metro apps (or Modern apps, or UWP apps, or whatever the hell they are called now), Microsoft specifically says tha

Funny enough, if you read the guidelines for Metro apps (or Modern apps, or UWP apps, or whatever the hell they are called now), Microsoft specifically says that you should offload all expensive operations to an async thread and keep the UI thread free so the interface can be quick and responsive. When I was making my first apps in university, they would routinely reject them from their app store saying the UI is not responsive enough. You'd think they actually care about efficiency and responsiveness. But then they hardcode a whole Documents directory scan right in the UI thread in their own damn voice recorder app. Unbelievable.