BABYMETAL

Good reaction and analysis.  BABYMETAL is a fusion of metal with Jpop aesthetics - and yes it is the three girls you saw in the video.  Their live band, the Kami Band, is made up of the best session musicians to be found in Japan and they can play anything.
The studio recordings do tend to be a bit over produced, especially Su-metal's vocals - they are at their very best playing live and that is where you will really hear the power in her voice, plus the backing of the Kami Band - and the live performance is what they are all about while losing absolutely none of the quality - if anything they improve on it.

They have about 50 songs and virtually none of them are the same.  They play almost every metal genre but will blend in many other musical styles and genres, so some may be a bit more pop leaning while others are straight metal, but they do everything in between and in one or two songs they will be at both ends of the scale at the same time.
They started in 2010 when they were aged 12, 11 and 11 and the whole idea was based around the lead singer's vocal talents and stage presence despite her tender years.  10 years on and they have gone from strength to strength and they fill arenas as one of the very best live acts in the world (and they have awards from international publications to say so, it isn't just my opinion).

'Megitsune' regularly tops fan polls for their favourite song and has been played live more than any of their songs.  This is really a female empowerment song.  It reflects a lot of the Japanese culture starting with the traditional instruments (shamisen) in the intro and the lyrics about women being compared to foxes (kitsune - which also explains why the fox masks were so prominent in this video) which in Japanese mythology are able to shape shift and take human form in order to deceive.  They are saying that women wearing their make up and hiding their true feelings are not trying to deceive anybody, they are simply trying to please everybody - so they are not kitsune (foxes), they are actresses and megitsune (female foxes or vixens) - and they are strong.

The breakdown with the pig squeals uses the exact melody of an old and very well known Japanese folk song called 'Sakura Sakura' (Cherry Blossoms).

When Su pulled the short blade (tanto) from her microphone (you may have missed that, I think you had your eyes closed) she said "Otome wa ... nametara ikan zeyo."  (Maidens ...  shouldn't be underestimated).  This is a famous quote from a Japanese gangster movie said by the daughter of a gang boss.

Much of the video was shot on location at the Asagaya Shinmei Shrine in Tokyo.  This has become a place of pilgrimage for BABYMETAL fans visiting Tokyo.

As a composer I suspect you will enjoy the more technical songs like 'Tales of the Destinies' (full on prog metal according to Mike Portnoy), 'Rondo of Nightmare', 'Amore' or 'Shine'.  Those are the songs I would recommend first for you.
Songs like 'Gimme Chocolate' get a different "WTF" reaction, they may be fun but you won't get so much from them until you are more familiar with what BABYMETAL are, so please don't jump at that just because it has most views.