Would it be ok to solder,brass or hard metal, to make table legs? Or Would the joint not be able to hold much weight?
Solder? Very unlikely. The bond is designed for electrical conductivity not physical strength (or, in the plumbing case, to achieve a certain strength via capillary action in a very small space). But brazing, that could work, if you have the capability to heat the metal, such as a forge. And welding of course is as strong as the metal you are welding itself.