How to make one leg longer on a metal table?

There are a few ways to make one leg of a metal table longer than the other, depending on what look you're going for and how much effort you're willing to put in. You can use a saw to cut the shorter leg down to size, or build up the longer leg with supports. You can also buy pre-made unequal-length legs from some hardware stores.
If you want to keep the table's original legs, you'll need to measure the difference in length between the two legs and cut the shorter leg down to size. To do this, mark the leg at the desired new length with a pencil, then use a saw to cut it down to size. Be careful not to make the cut too short, as you won't be able to make it longer again without buying a new leg.
If you're willing to put a bit more effort into the table, you can build up the longer leg with supports. This will add height to the table, so make sure there's enough clearance beneath it before starting. Cut some pieces of wood to size and screw or nail them into the longer leg, making sure they're level with each other. You can then cover the supports with a piece of wood or metal trim to give the table a more finished look.
If you don't want to deal with cutting or building up legs, you can buy pre-made unequal-length legs from some hardware stores. These are usually adjustable, so you can set them to the exact height difference you need.
No matter which method you choose, making one leg of a metal table longer than the other is a relatively easy process. Just be careful not to make the table too lopsided, as it might become unstable and unsafe to use.