I want to know can we declare the events as static if yes why and application of such declaration.
Sample please as seeing is believing
Yes, you can. See, for example, Application.ApplicationExit. Note, however, the warnings on that page about memory leaks when attaching to static events; that applies to all static events.
There's nothing magical about when you use them: when you need to provide an event for a static class or an event that deals exclusively with static data and it makes sense to implement it this way.