For some reason, The Beach Boys make a point of mentioning in the chorus of Little Saint Nick that "Christmas comes this time each year."
The Beatles, in "Come Together", gave us such enlightening information as "He's got feet down below his knees" and "One and one and one is three". You don't say.
They gained the grand prize for this trope in "All You Need Is Love", in which everything except the "all you need is love" sentiment is basically saying "anything that humans are able to do, humans can do."
Nothing you can do that can't be done, nothing you can sing that can't be sung
In concerts, to introduce the song "I Cum Blood," Corpsegrinder says "this song is about shooting blood out of your cock."
David Bowie's 2013 single "Where Are We Now?" features the line "the moment you know, you know you know". It makes sense, given the tone of the overall song, but still sounds remarkably obvious when its actually said aloud.
So Yesterday by Hilary Duff states that "If the light is off, then it isn't on" and "You can change your clothes (if you wanna)". No, really?
Jonathan Coulton in "Betty and Me", on the subject of genetically engineered children:
And although it was expensive, it was legal in the states where it wasn't banned.
He also does this at least once in "Madelaine":
If it doesn't kill you, it'll make you stronger But if it kills you, you'll be dead
Daniel Amos's "Autographs for the Sick" (from Doppelgänger) starts off with several voices speaking foreign-sounding gibberish and an interpreter translating into English. At the end, one of the voices just sings a line in English, and the interpreter helpfully translates that, too. And then:
Speaker #4: Hahaha... Interpreter: Ha ha ha. [three drum beats] Interpreter: Dit dit doo.
Lee Ann Womack's song "Liars Lie", after catching her lover trying to lie, the narrator sings:
Lil Wayne seems to like being Captain Obvious. For example, in I Can Transform Ya he says, "I Can Transform Ya/ Like a Transformer". In Mrs. Officer the guy singing the chorus sings, "I can make you say, Wee-ooh-wee-ooh-wee, Wee-ooh-wee-ooh-wee" and Lil Wayne chimes in with, "Like a cop car".
Los Bravos helpfully informs us, "Black is Black".
The background singers in Manfred Mann's "The Mighty Quinn" at one point carol, "We're singin' a song!"
The Simon & Garfunkel song "The Boxer", when performed in concert, usually includes an extra verse that contains the line: "I'm older than I once was and younger than I'll be. That's not unusual." Is this a lampshade or an intensifier?
Likewise, his song "You Don't Love Me Anymore", in which he expresses that he gets the impression his significant other, well, doesn't love him anymore, citing reasons for his suspicions such as poisoning him, holding up a knife, putting piranhas in his bath again, etc.
The song "All or Nothing'' by Whitesnake includes the line "My heart is burning/And the fire is hot".
2 Chainz. There are so many examples, but let's just go with the most famous one:
The classic '60s love song Baby I'm Yours (first recorded by Barbara Lewis) has the narrator say that he/she is "yours" until a number of impossible events happen (until the stars fall from the sky, until 2+2 is 3), then helpfully elaborate "In other words, until I die/the end of time/eternity."
Forever Young from the second Care Bears movie includes the line, "You'll be with me until/The sun shines through the night./It never will."