The Modal word "will" is used to express future events and must be in the proper sequence if other auxiliaries are used.
Another important Auxiliary are the Modals. They do a hodge-podge of things including express future events. For example, "I will go." The word "will" is a modal.
You can combine Auxiliaries to express nuances of time. For example, "I will have gone." (Notice that "...one" in the word "gone" is an allomorph of "...ed," (as in jumped) and many children struggling with this concept might use the word "goed,' instead of "gone.")
You can even add the Negative Auxiliary and the Progressive Aspect to say, "I will not have been gone very long." Notice how delicate the word order is here. Which of the following is acceptable:
- "I not will been have gone..."
- "I been will not have gone..."
- "I will have not been gone..."
- "I been have will not gone..."
- "I have not will been gone..."
- (Answer--The third sentence)
How does anybody learn this! Try explaining the proper word order to a deaf child.