1 US gallon = 3.78541178 liters.
Only (!) if you mean pure water, then 1000 litres of water weigh 1 metric tonne.
1000 litres of water are 264.172052357 US gallons that weigh 1 metric tonne.
Don't use this conversion for gasoline.
There are approximately 312 gallons of D2 diesel fuel in one metric ton. This can vary slightly depending on the density of the fuel.
There are approximately 264 US gallons in a metric ton of seawater.
Approximately 272 gallons of coconut oil make up 1 metric ton.
1 metric ton of water is equal to 264.172 gallons.
About 317 gallons of heavy fuel oil are in a metric ton.