When to use @using in my razor syntax view in ASP.Net MVC 5

And yes, I searched it on google I could not find the exact answer.

So, When to use @using SomeModel in my razor syntax view. I am new to ASP.net MVC 5 and I know that each view can be strongly bound to a model or a viewModel and we use @model ModelName. What will be the situation when I will have to use @using in my razor view. Any example would be highly appreciated.