shall疑问句可用于第一人称和第三人称
例句具体看书

用于第二、三人称陈述句中
1、表示“命令” 在法律条文、规章制度中，与must意思接近，主要用于第三人称。
2、表示说话人的许诺。用于第二、三人称。
you shall have the money back next week.= i promise you will have the money back next week.
3、表示强烈的意愿、威胁。

he shall be punished if he disobeys.若他不服从，定将受到处罚。
you shall pay for this 你一定得为此会出代价

may 表示让步
may...but 结构

we may have our differences from time to time,but basically we trust one anther's judgment. 可改为：
we admit that we have our differences,but basically we trust one another's judgment.
或although we have out differences,basically we trust one another's judgment.
不能改成it is possible that we have our differences,but basically we trust one another's judgement.
这时的may已经失去"可能"的含义，认为是真实的陈述.

还可以用在让步状语从句中，例句看书。