Full Metal Tank

[DaveH]

I have a metal tank I was wondering what can I fill it full of to make it lighter (less heavy).

PS it's a riddle

Dave

 

[Stosta]

I have a metal tank I was wondering what can I fill it full of to make it lighter (less heavy).

PS it's a riddle

Dave

Helium?

 

[GregF]

holes

 

[DaveH]

holes

Well done @GregF

Dave

 

[craigb]

filling it with butane could turn it into a lighter