Was first to make that heavy metal sound (3)
I believe the answer is:
led
'was first' is the definition.
'that heavy metal sound' is the wordplay.
'that heavy metal' becomes 'lead' (I've seen this before).
'sound' shows a homophone (sound like).
'lead' sounds like 'LED'.
'to make' is the link.
(Other definitions for led that I've seen before include "Went ahead" , "Went first to show the way" , "Went at the head of others" , "Came first" , "Shown the way" .)