When Motorhead started out, nothing was called 'heavy metal' or 'metal.' Back then it fell under the 'hard rock' label along with groups like Black Sabbath, Led Zeppelin, Heart etc. For those who remember when the term 'heavy metal' started getting used, those same 3 groups I mentioned were now called 'heavy metal'.
Anyway, some labels actually hurt the band once they are associated with them. Remember 'grunge,' 'alternative,' etc. Anyway labels are a form of marketing and most professional musicians/rock stars that I know, don't like being called by what people or the record companies have labeled them.