When there is no event sequence, the event present generally sounds inappropriately ‘stagey’ or theatrical. We can compare the following as two ways of describing the same action:
I open the cage. | I am opening the cage.
The second sentence, which contains a Progressive verb form, is a natural description in answer to the question What are you doing? But the first sentence is rather dramatic, because it implies the total enactment of the event just at the moment of speaking. If spoken, one would expect it to be accompanied by a gesture or flourish; in writing, it seems incomplete without an exclamation mark. The event use of the Present is generally the ‘marked’ or abnormal alternative to the Progressive Present, because there are few circumstances in which it is reasonable to regard an action as begun and completed at the very moment of speech.
a. However, the event present does occur exceptionally in ordinary speech in exclamations such as Here COMES my bus! and Up we GO!
b. The stagey quality of the event present is evident in its employment in old-fashioned theatrical language (not used in present-day English except in fun): The bell tolls! He yields! The spectre vanishes! etc.
Chapter 1 - Leech, Geoffrey N. 2004. Meaning and the English Verb. Harlow, England: Pearson/Longman.
When I was reading this part I felt confused about the stagey or dramatic effect of the present tense. I cannot envisage how it's used in old-day English or in fun. Perhaps I'm short of some imagination (a few GIF pictures could make for a better understanding). Those bolded parts are not specific enough for me. Please help to clarify them.