MusiXmatch is a free Chrome extension that will provide karaoke-style lyrics to most YouTube music videos. It can be used very easily on desktop and mobile devices.
Using songs, and using lyrics karaoke-style, is a longstanding and effective language-learning strategy, and you can read about many of them at The Best Music Websites For Learning English.
You can read more about it at TechCrunch.
I think MusiXmatch is a great tool. However, they’re advertising it with a video that pretty much tells you nothing about it, and may be one of the dumbest videos put out by at tech company. Because it’s so weird, I couldn’t resist embedding it below, but don’t plan on learning anything about how it works by watching it: