Question

A man is like steel when he loses his temper he is worthless meaning

Answer 1

The saying
"men are like steel, when they lose their temper they lose their worth?" means that a man in a rage has lost a valuable property (the ability to keep a cool head) just like steel looking it's valuable property (it's tempering) when it gets re-heated.
The expression tell men that they should not lose their "temper".