Change Genre Metal by Heavy Metal

Hi,
When i use the task to REPLACE The %genre% Metal with Heavy Metal it work only for My Metal genre but it mess-up the rest. The Heavy Metal genre become Heavy Heavy Metal.
I would likw to keep the others like Power Metal, Trash Metal, Heavy Metal intact.

Use a filter
%genre% IS Metal
and treat only the matching files.

Or use an action of the type "Format value" for GENRE
Format string: $if($eql(%genre%,Metal),Heavy Metal,%genre%)

Thats because your search word "Metal" is not only included in
Metal
but also in
"Avant-garde Metal"
"Black Metal"
"Doom Metal"
"Heavy Metal"
"Speed Metal"
and so on...

And all these occurrences of the word "Metal" will be replaced by your new two words "Heavy Metal".

As @ohrenkino explained:
First filter for those GENRE that contain only the single word "Metal" and nothing else.
Then select those filtered tracks and use your replace function.