Problems between camera and size of objects

Hi everyone!
First sorry for my english, i have a bad english, but i will try to explain my problem cleary ^^.

I have a problem with my camera and the field of view in unity.

The problem is: i have a cube in my scene, and my camera is in front of this cube.
When i try to modify with my mouse the width and the length of the windows, and when i try to change the resolution, sometimes some parts of the cube is out of the screen.

I would like to have the same point of view when i change my resolution.

I don’t know if you understand what i say ^^, but if somebody have a solution it could be very useful!

Thanks everyone!

When you change from resolution A to resolution B, do they have the same aspect ratio- the same shape?

Hi spoonman2! Thank you for your answer.
Yes i have the same aspect when the ratio is the same.