Conditional clause Main clause
1. If + Present Tense will + inf / present tense / imperative
If you help me with the dishes (if + pres),
I will help you with your homework. (will + inf)
If the sum of the digits of a number is divisible by three,
the number is divisible by three (Pres. tense)
If you see Mr Fox tonight, tell him I am ill. (imperative).
2. If + Past Tense would + inf
3. If + Past Perfect Tense would have + past participle
We do not normally use will or would in the conditional clause,
only in the main clause.