Vomit smells like metal and food wasnt digested why?

This could be due to an infection in the GI tract. Most often, they are viral infections-viral gastroenteritis. It will run its course so the most important treatment is to keep the child hydrated to avoid dehydration. Once the nausea/vomiting stops, a bland diet should be given. The BRAT diet is a good way to have the child start eating again. Call pediatrician if symptoms continue or worsen.