Clean the Trunk
The first step is to clean the trunk. Since it is old, there is a good chance that it will have rust on it. Sand it down with light grade sandpaper and then use a rust buster solution for whatever is left on it. Once you are done, use a soft cloth to remove any residue.
Paint the Trunk
Select a colour of your liking and paint the trunk. Ideally use a dark colour such as black or brown. This colour will give it a feel of wood that will look great. You can also make a bit of a pattern to make the table look even better. You can use masking tape while you paint to add different shades to the table. Make sure to mask the metallic parts of the trunk or suitcase are covered with the masking tape so that they don't get stained.
Add the Legs
Get wooden legs for the base of the table. Fix in the bases for the legs by drilling small holes in the bottom of the tables and attaching it with screws. Add the legs using super glue. Make sure that they are attached properly before resting the table on these legs. You can paint the legs with the same colour which will give the table an even look. You can also try to mix and match by using contrasting colours on the legs.