Matthew McConaughey said he shaved his head, gained 45 pounds and wore false teeth to make himself even uglier than usual for the character. He claimed he gained the weight by eating cheeseburgers and drinking lots of beer and milk shakes.
During an interview on ESPN's First Take, Matthew McConaughey claimed this was his favorite role he has ever done.
"Gold" is based on the Bre-X scandal of the 1990's. Bre-X was a Canadian company. The bar where Wells and his company hang out is called "The Three Greenhorns." This is the name of a real restaurant (not bar) in Vancouver, BC, Canada (The Three Greenhorns were, famously, three of the earliest homesteaders in Vancouver). Although the company has been moved to Nevada, the writers kept the name of the restaurant.
Paul Haggis was interested in directing this after seeing a sample of Patrick Massett and John Zinman's script, but passed in favor of other projects. He showed the sample to Michael Mann, who bought the script intending to direct it, with he and Haggis producing. Mann dropped out after deciding to make Blackhat (2015) instead. Spike Lee was later briefly attached to direct before Stephen Gaghan signed on.