If restated, the sentence, that would best replace 'As a conductor of heat and electricity, aluminium exceeds all metals except silver and gold.'

Silver and gold are exceeded only by Aluminium as conductors of heat and electricity

With the exception of aluminium, silver and gold are better than any other metal as conductors of heat and electricity

Silver and gold are better conductors of hear and electricity than aluminium is

Aluminium is a better conductor of heat and electricity than silver and gold