>>> Thanks to... W3Schools :

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    function callNumbers() {

      // Call the Numbers API for random math fact
      let url = "https://api.metalpriceapi.com/v1/latest?base=USD&currencies=XAU,XAG&api_key=Dxt3fx5NcET88EGsAtvrdJ";
      let fact = UrlFetchApp.fetch(url);

      let apiResponse = JSON.parse(fact.getContentText());
      Logger.log(apiResponse.timestamp, apiResponse.rates.XAU);

      let sheet = SpreadsheetApp.getActiveSheet();
    //   sheet.getRange(1,1).setValue("timestamp");
    //   sheet.getRange(1,2).setValue("rates");

      sheet.getRange(sheet.getLastRow() + 1,1).setValue(apiResponse.timestamp);
      sheet.getRange(sheet.getLastRow() + 0,2).setValue(apiResponse.rates.XAU);

    }

Function Call trigger