虚拟语气是一种动词形式，表示说话人的一种愿望，假设，怀疑，猜测， 建议等含义，虚拟语气所表示的含义不是客观存在的事实。
If I were you, I'd take them away.
如果我是你的话，我就会带走他们。
If I had met Li Hua, I could had told him.
如果我碰见了李华，我就告诉了他了。
If I had time. I could come to help you.
如果我有时间，我会来帮助你的。
He suggested that our class should be divided into five groups.
他建议说我们的班应该分成五个小组。
He speaks to us as if he had been there.
他给我们讲的好象他去过那儿。
虚拟语气的用法
1) 虚拟语气用在简单句中，表示祝愿，命令。
May you be happy.
祝你幸福。
May you have a good time.
祝愿你玩的痛快。
May the friendship between us last long.
祝愿我们的友情天长地久。
Have a good journey!
祝愿你旅途愉快！
You go out！
你出去！
2) 虚拟语气用在宾语从句中。动词 wish, suggest,order,insist, propose,等词后面的宾语从句表示的是一种虚拟语气， 宾语从句中的动词动作表示的只是一种愿望，要求。
I wish she would be on my side.
我希望她能站在我一边。
I wish I could help him.
我希望我能帮助他。
He insisted that all of us should be there on time by any means.
他坚持要我们大家想尽办法按时去那儿。
动词 demand, suggest, order, insist, propose 后面的从句中，"should" 可以省略。
The teacher suggested that we (should) clean the blackboard after class.
老师建议我们课后把黑板擦了。
He ordered that the students wash the clothes every week by themselves.