在cannot but, do nothing but (except), had better, had best, rather than, would rather…than, had rather…than，would sooner… than 和would as soon…as等结构后要求接不带to 的动词不定式。

【例句】

I cannot but admire his courage. (我不得不佩服他的勇气。)

I have done nothing except do what I should.

You had better do it yourself.  你最好自己去做。

这个had better 和would rather及may as well 差不多都是同义的。

I had (或would) rather die than yield.

= I had (或would) sooner than yield.

= I had (或would) as soon die as yield.

我宁死也不投降。

还有一些固定搭配，黎老师已经说了，我就不重复了。