If you leave late, you will miss the train. - Se você sair atrasado, perderá o trem
If A happens, B will happen.
The first conditional is used to express future situations where a result is likely or possible but not guaranteed.
If + simple present + future simple
|A quick summary of the first conditional.||Wall Street English|
|An overview, explanation of 'when' vs. 'if' and some further tips for using the first conditional.||Smrt English|
|Some examples using the first conditional.||TeacherIHaveAQuestio|
|How to use the first conditional.||BBC Learning|