Heavy, malleable metal (4)
I believe the answer is:
lead
This clue is a double definition.
'heavy' is the first definition.
(thesaurus)
'malleable metal' is the second definition.
(I've seen this in another clue)
(Other definitions for lead that I've seen before include "Guide by going in front" , "Guide the heavy metal" , "Metal - van - go ahead" , "Be in charge of, element" , "Metal - wire" .)