How many gallons in a metric ton?

Answer 1

There can be no equivalence. A ton is a measure of mass. A gallon is a measure of volume. The two measure different things and, according to basic principles of dimensional analysis, conversion from one to the other is not valid.
If you are not convinced, consider a gallon of air. How many tons? Next consider a gallon of [molten] lead. How many tons?
The masses of equal volumes of the two substances will clearly be very different. So there is no direct conversion between mass and volume: you need to know the density of the substance to enable you to carry out the conversion.

Answer 2

There are about 264.2 gallons in a metric ton. This can vary slightly depending on the substance being measured, as different substances have different densities.