Most brokers label spot gold XAUUSD, but GOLD, GOLD.p, XAUUSD.pro, XAUUSD.r, XAUUSDm and #Gold all appear depending on the account type. Gold sits in the Metals or Commodities folder in MT5 Market Watch, not under Forex.
Open Specification on the gold symbol and read contract size, digits and tick size, minimum volume and volume step, swap long and short, and the trading sessions before your first trade. Contract size of 100, 10 or 1 ounce changes every lot size you calculate.