How do acids affect on metal?

To some extent, yes and they release H2 gas after the reaction.

it affects metal because the fluids from acid are very hot and they can dissolve the metals strong layer and can create damage such as rust. I did this project in third grade two years ago.

Usually acids are known to affect metals. this rule applies for acid + metal reactions. An acid + a metal reacts to give a metal salt + hydrogen Eg: Zinc + Hydrochloric acid reacts to give zinc...

Phosphoric acid combines with iron oxide (rust) to form iron phosphide, which is inert - it doesn't corrode any further. The most common product made of phosphoric acid for this purpose is called...