MacBook Pro won't start

[KitKatKatelyn]

So I'm in the middle of exams and I really need my Mac to work. Every time I go to turn it on my Mac freezes and the loading bar doesn't make it to the half way mark. I've tried multiple solutions but unfortunately my computer continues not to load anything. I really don't know a lot about computers so please bare with me!

 

[CoastalOR]

So I'm in the middle of exams and I really need my Mac to work. Every time I go to turn it on my Mac freezes and the loading bar doesn't make it to the half way mark. I've tried multiple solutions but unfortunately my computer continues not to load anything. I really don't know a lot about computers so please bare with me!

Sorry for your troubles at such a inopportune time.

There might be more assistance responses with some more information.
Where there any symptoms or changes before your startup problem?
What model/year Mac?
What OS?
Any backups available?

Here are some startup key combinations you might try to see what happens:
https://support.apple.com/en-us/HT201255