Conditionals are ‘if’ phrases. They can be used after main clauses, but are frequently used as openings to sentences.

I will go to the party if I have time.
= If i have time, I will go to the party.

He would have dated her if he wasn’t already married
= If he wasn’t already married he would have dated her.

Examples of Starting a Sentence with a Conditional

If only he had met her earlier, he would have married her; unfortunately, he was already taken, stuck with a wife he didn’t love.

If that is the best he could do, then there was no way the boss was going to hire him.

If the sun ever set on this relationship, Dave knew it would be his fault.