I'm building a steel type deck, and I want a card that can retrieve Steel Energy from the discard pile. I found two cards, Magnezone and MetagrossGX. Which one would be better for a deck?
MAGNEZONE: https://www.pokemon.com/us/pokemon-tcg/pokemon-cards/ss-series/swsh10/107/ METAGROSS: https://www.pokemon.com/us/pokemon-tcg/pokemon-cards/sm-series/sm2/85/
Also, what is a Pokemon/trainer card that's good at obtaining steel energy from the deck?
As JustATypicalPerson pointed out, since you are looking for a card to get Metal Energy from the discard pile specifically, Metagross is the Pokemon to go for. However, Metagross is not the only card that can recycle Metal Energy. There are others such as the Energy Retrieval, Brock's Grit, Rayquaza from Guardians Rising, and Munchlax from Unified Minds. These are just some examples. But if you want more, here are a couple Google searches I did;
https://www.google.com/search?q=Metal Energy recycling TCG https://www.google.com/search?q=Metal energy acceleration
As far as getting them from your deck though, you can try using a Mallow, Energy Spinner, Energy Loto, Solgaleo GX from Sun & Moon, a Red & Blue, or even the Magnezone you mentioned. Again, here are some links; https://www.google.com/search?q=Tcg energy search cards This is all I know about this. I hope it was helpful and good luck on that deck!