One rock band that I enjoy, and think would be good for Japanese learners is: 打首獄門同好会 (Uchikubi Gokumon-Doukoukai)
The songs are just about every day life, and the lyrics are written simply. At my current level, I often find that I can't follow the lyrics to most Japanese music, but with Gokumon songs I find that I can follow a lot of it, which is a rare treat.
I dunno if it's been mentioned yet, but Japanese city pop is really good if you like 70s/80s style funk/pop. Lots of nice guitar and saxophone solos, and great for chilling/dancing/studying. It's easy to find all over youtube too. A lot of people report a nostalgic feeling listening to it, despite never loving in 80s Japan, and I totally get it.
Tatsuro Yamashita, Mariya Takeuchi (they're married!), Miki Matsubara and Takako Mamiya are my favourites. A lot of nice mixes out there on YT to check out to find more artists. Tatsuro has a few english songs too, so you can sing along the them if that's your native language!
I see no one has mentioned Wagakki Band yet. They're my favorite band ever, it's like traditional old fashioned Japanese music combined with rock or pop and other genres. They have too many great songs to name.
Somehow it seems like no one mentioned Baby Metal? But I guess everyone knows them so there's not really a reason to. I only know several of their songs, Megitsune is my favorite.
Otherwise I don't really know any others very well, exept from anime intros. (And composers, but that's a whole different story)
i recently found 新しい学校 on youtube, now i'm obsessed with them. it's a girl group with four members that creates music in such genres as japanese rock and pop (their new songs are mostly japanese pop, but those, which are older is rock, as i mentioned). i would recommend to try listen their music, it's really good.
not a Japanese band, but a Japanese composer so i don't know if he counts, but kenshi yonezu makes really good songs. my favourite song by him is uchiage hanabi. i think he sometimes sings in his songs as well.
it's a girl group with four members that creates music in such genres as japanese rock and pop (their new songs are mostly japanese pop, but those, which are older is rock, as i mentioned). i would recommend to try listen their music, it's really good. 