Liter is a unit of volume equal to 0.001 cubic meters. Metric ton (tonne) is a unit of mass, equal to 1000 kilograms. The only time you can find mass from volume, is if you have a specific substance...
The question, as stated, cannot be answered sensibly. A gallon is a measure of volume, with dimensions [L3]. A ton is a measure of mass, with dimensions [M]. The two measure different things and...