If + present simple + future simple
If you don't know me by now, you will never know me (Simply Red)
We can use a modal verb in the if sentence
I can't help you if you don't help yourself. (Amy Winehouse)
(Listen to the song and find a grammatical mistake)
In the main sentence, an imperative can be used instead of a present.
If you need me, call me (Marvin Gaye - Ain't no mountain high enough)
If + past simple + conditional simple(would + bare infinitive)
What would you do if I sang out of tune? (Joe Cocker / The Beatles)
If I were a rich man
If I were a rich man,
Ya ha deedle deedle, bubba bubba deedle deedle dum.
All day long I'd biddy biddy bum.
If I were a wealthy man.
I wouldn't have to work hard.
To be continued ....