Lord Gold was once a human, and the richest man in the world, but his greed for gold led to him becoming literally greedy for gold - he could eat nothing but gold, and then he turned into a demon with gold skin and clothes known only as Lord Gold.
Likewise for his two minions, who became Lord Silver with a silver face and clothes, and Lord Nickel (though his appearance is more generically bronze-y-copper-y). Together these three make for a trio of memorable antagonists, with simple-but-effective makeup and colour-coding.
Unfortunately for Lord Gold, his chief follower Silver is a Starscream, plotting to usurp his position by poisoning him (with iron pyrites - fool's gold) and marrying his daughter against her will.
It is into this situation that Monkey and the others wander. Pigsy and Sandy are captured and put to work in Lord Gold's mine. Monkey goes looking for them and, while disguised as a horsefly, is hit on the head and the resulting injury helps keep the episode from being half the length it is.
Tripitaka is then captured (naturally. By the way Yu Lung isn't in this episode and the horse hardly features, meaning this episode would feel very much like it belongs in the first season except for the presence of the second Pigsy) and taken to Lord Gold.
Because Tripitaka is the only man he has found who resists the temptation of great wealth, Lord Gold is convinced the priest is the right man to marry his daughter. Of course neither of them wants that, so Lord Gold has them both put in prison.
Monkey eventually leaps into action and rescues them from prison, and then goes about putting everything to rights, saving Lord Gold from Silver's coup.
The story concludes with a bizarre epilogue showing a human-looking-but-giant Lord Gold breaking up mountains ("it's only a model") and eating dirt, as the narrator explains that this was his penitence to return him to the wheel of karma.