动名词开头的句子可以作主语，具体如下：
直接位于句首做主语
Swimming is a good sport in summer.
Reading is an art.
Climbing mountains is really fun.
用 it 作形式主语，把动名词（真实主语）置于句尾作后置主语
It is no use telling him not to worry.
It is a waste of time persuading such a person to join us.
用于“There be”结构中
There is no saying when he'll come.
There is no joking about such matters.
用于布告形式的省略结构中
No smoking.
No parking.
动名词的复合结构作主语
Their coming to help was a great encouragement to us.
It is fun playing with children.
比较动名词和动词不定式作主语
Smoking is not good for health.
It is not good for you to smoke so much.
建议
动名词作主语时，谓语动词通常用单数形式，如“is”、“are”等。
在某些固定句型中，如“It is no use/good/a waste of time...”等，通常使用动名词作真实主语。
动名词可以表示泛指或抽象动作，而不定式多用来表示特指或具体动作。
通过以上例句和说明，可以更好地理解和运用动名词作主语的语法结构。
