If it is raining and you don't have an umbrella,... (will)
If it is raining and you don't have an umbrella, you will get wet
If your teacher gives you homework,... (have to)
If your teacher gives you homework, you have to do it.
If you visit Bilbao,... (should)
If you visit Bilbao, you should try lots of different pintxos.
If you do lot's of sport,... (will)
If you do lots of sport, you will get healthier
If you study for your exam,... (will probably)
If you study for your exam, you will probably pass it
If you go to Paris,... (should)
If you go to Paris, you should visit the Eiffel tower
If you live near your friends,... (can)
If you live near your friends, you can hang out with them
If you have the flu,... (should)
For example: If you have the flu, you should stay at home
If it's the weather is good,... (can)
For example: If the weather is good, you can play outside
If you only eat junk food,... (will)
If you eat a lot of junk food, you will be unhealthy
If you are tired... (should)
If you are tired, you should go to bed
If you want to learn English,... (have to / should)
If you want to learn English, you have to study and speak in English as much as possible
If you are really tired in school,... (probably won't)
If you are tired in school, you probably won't learn much