Am I able to use movie posters in my website for commercial gain?

Hi, I wonder if anyone can help me on here. I am new to WordPress and I wish to have a movie review website. With this, I will need to use certain images and film posters from a specific site; ImDb, Youtube, Rotten Tomatoes etc. I understand that small use of these images may fall under “fair use”, although for commercial gain is where I don’t understand it. For me to make money from my website in the future, what steps do I need to take to ensure I am not breaking any law? Do I need to obtain permission from these major websites? If so, how do I go about doing that? There must be a way for me to be able to make a profit from my website, use movie posters/trailors etc and not break any laws???

Any update on this would be very appreciated as I am desperate to move forward.

Thank you!