When to solder fold formed bends

I was told by my instructor that if I make a scored fold (like
making a box) that I have to solder the inside of the crease. True?
Is so, then do I have to solder fold formed bends?

thanks,
brenda

You do not always have to solder. I do if I am going to shell form a
piece after the fold so the seam will hold together. The kind of
fold you are doingand the thickness of the metal and the end design
will depend on if you need to solder. Oh and scoring, in my
training, thins the seam so soldering is usually required.