Yes, they can. As the food is ground down and eaten, some small pieces fall through and pre-weaned and weaned rats will start on those pieces. My weaned rats are typically 70 to 90g, and reach no problem by 3 weeks, which is before I wean.
I've never heard of adults chewing through the metal. Plastic or wood is where people are generally concerned.
Get good stock to start that are not tub/cage chewers and you will not have an issue there either way.
Sent from my SM-G950U using Tapatalk