It is likely that he will come.为什么这句话不对?

不对,补充一下,刚刚讲的漏了,因为 Likely 表示 “某人很有可能做某事”时,即对人的行为进行推测,用的句型是 sb is likely to do sth,即句子的主语要是人,而楼主的句子 it is likely that后面跟的是他很可能回来,即某人很可能做某事,就是错的,当要用it 做主语的时候,可以采用 possible 的这个句型：it is possible that （当时我高三的时候老师就是这么坚定不移地和我们讲的）
即：sb is likely to do sth
it is possible that
如：he is likely to pass the exam.
It's possible that he will pass the exam