The best way to learn proper English is to read news report, and watch news on TV. Watching TV shows is a great way to learn casual English, slang words, understand culture reference and humor. If you have already watched these shows then you may recall the words used in the following dialogs.

...and silk, and STEEL.
Game of Thrones Season 1, Episode 8

...the arakh won't get through the STEEL.
Game of Thrones Season 1, Episode 3

Are you sure? It's Valyrian STEEL.
Game of Thrones Season 7, Episode 4

Valyrian STEEL.
Game of Thrones Season 4, Episode 4

There are three living smiths
who know how to rework Valyrian STEEL.
Game of Thrones Season 4, Episode 1