英语if语法?就是IF后面如果加动词要什么形态?还有其他的一些用法是什么?

if 引导的从句较多,个人以为一般状语从句较简单,而虚拟语气比较复杂,所以简单写了点虚拟语气用法.
if 虚拟用法
1、对将来虚拟 if +did/were to /should , .would/could /might +do
其中 were to 和should 可以倒装
例如：If it were to rain = Were it to rain
If it should rain =should it rain
2、对过去虚拟if + had done,.would + have done
倒装 Had it done .
例外： If i had followed his advice ,i would not be in such trouble .句中用be 而非 done是因为现在处于困境中
3、对现在虚拟 if +did ,...would /could /might +do

conj.
1. (表示条件)如果
He will come if you invite him.
如果你请他,他会来的。
2. (表示虚拟)假如,要是
If I were you, I would never do that.
如果我是你,我决不做那件事。
3. (表示让步)即使
We'll go even if it rains....

最重要的就是if后面不能够跟将来时，都是用一般时来表示将来时。

if引导条件状语从句，主句可以是将来时，祈使句，或用情态动词引导的句子，从句可以是一般现在时。