Though the bands music strongly defines itself as metal it stands out from all the other similar bands by their signature element of having two lead vocalists. That element itself isn’t reinventing the wheel type a thing but once the vocals are clean and performed in a perfect harmony, it's a totally different thing. That along the fact that Mournful Lines plays their signature metal with a much lighter sound separates the band from their competitors. Once the band hired their first female vocalist, the band got a wider perspective on how to make metal distinctively due to her having such a strong background in pop music.
Lyrics are commonly revolving around topics such as suicide, depression, domestic violence, cheating and self-hatred but there also is a sentimental side to their lyrics too - love, but committed to their melancholic side, the love is portayed from a negative perspective hence the name for the band.