Later in Sept, I believe there was a copyright/trademark disputed and Microsoft was forced not use name term “metro style” anymore and the Metro Style apps were changed to Windows Store apps.
But what I am still seeing is, developers are still calling these apps, Windows 8 apps. I understand these app target Windows 8 operating system but it does not mean they won't work on Windows 9 or beyond. I see some authors are still using term Metro Style apps.
C# Corner has many articles and tutorials on Windows Store apps. Check out Windows Store apps here >>