I assume you are talking about silver soldering - not soft
soldering. You can solder bronze, brass, steel etc in much the same
way as you solder silver, but aluminium is a different matter. First
off, it’s melting point is too low to use normal silver solder - it
melts before the solder. Second,it oxidises in a few seconds at room
temperature and the oxides are impervious to most normal fluxes.
Special fluxes are available, as are special solders, but generally
speaking, aluminium is difficult to solder. Google "solder aluminium"
Regards, Gary Wooding