You might as well throw your money into the sea as lend it to Ken.

You may well be surprised at the news.

I would rather go out than stay home. I would rather not go to church.

We used to go fishing in the lake. There used to be a hospital on that hill.

This knife is used to cut apples. I am used to cutting apples.

You need not have come at 5 o’clock You should have seen the view. Ken may have left for Tokyo yesterday He must have mistaken me for my cousin Jim cannot have written the poem by himself.

You had better go to the office at once. You had better not attend the meating. You had best leave now. You had best not sit up late at night 「had betterは、時に忠告・命令の意味を表す強い表現になるので、目上の人には使わないほうがよき」