1.介词后面一般加名词或动词的ing 形式.
There is a cat under the table. (under +the table).
We may go out for a walk instead of staying at home.(of + staying).
2.be 后面加名词,形容词 ,不定式, 动词ing 形式 或 动词的过去分词
I am a student.
He is tall and strong.
His aim is to pass the exam.
They are playing football on the playground.
Paper is made of wood.
3.情态动词后面一般加动词原形
We can sing English songs.
You may stay here now.
She must study hard.
学习英语主要靠平时积累,不能仅仅想通过一些规律来学好英语.

祝您进步!