It depends on what you like. If you are more into rock/animeopeninghah music, then I'd recommend DAY6.
Groups I PERSONALLY like to LISTEN are: WINNER, NCT127, MONSTA X, EXO, K.A.R.D, GOT7, BTS. Though I mainly listen to artists like Dean, C Jamm, BeWhy, IU and many more buuuut I think it's more like khiphop But if you are into that - just hmu, I have a playlist just for that.
There's a difference between groups I like to LISTEN to and groups I STAN. For example, I stan BIGBANG, even though I don't really ever listen to their music haha. The opposite with BTS - I'm not really a fan of them as a group, but I really do like their songs. So asking for opinion on forums like these is kind of useless, since people are going to suggest you the groups they stan. I think you should find it for yourself, cause everyone's different.
BUT IF YOU WANT MY PERSONAL FAV THEN I AM AN EXTREME FAN OF GOT7, EXO, I.O.I, MONSTA X, MAMAMOO, RED VELVET, SF9 SO YEAH GO CHECK THEM OUTTTTT AND GOT7 IS HAVING A COMEBACK THIS MONDAY MARCH 13TH SO DON'T MISS OUT AND STAN GOT7 HELLYEA