The 1985 lawsuit from bluesman and Chess Records star Willie Dixon ended with a cash settlement. Court ruled his song You Need Love was taken for Zeppelin’s Whole Lotta Love. Dixon’s name added to the credits after that.
Controversies:
The Lemon Song. Lawsuits resulted in Howlin’ Wolf (Chester Burnett) getting back royalties for his Killin’ Floor which is nearly identical.
Babe I’m Gonna Leave You – A song written by folk singer Anne Bredon, which was popularized by Joan Baez. Zeppelin put “Traditional arr. Page.” Said Baez did so earlier. Decades later, Bredon was made aware of the Zeppelin song, and won a large back-payment of royalties. Since 1990, the song has been credited as “Bredon/Page & Plant”
How Many More Times – A medley piece comprised of sections that are either inspired by or direct replicas of Howlin’ Wolf’s “How Many More Years,” Albert King’s “The Hunter,” and Jeff Beck’s “Beck’s Bolero.” The original credited just Zeppelin, but this has since been amended to include Howlin’ Wolf’s name.
I Can’t Quit You Baby – A classic Willie Dixon blues tune, has always been properly credited to Dixon.
Black Mountain Side – A Page instrumental, similar to the earlier “Down By Blackwaterside.” by Bert Jansch. The song was taught to Page by Al Stewart, who worked with both Page and Jansch.
https://www.youtube.com/watch?v=TScCqHlBag0
Willie Dixon’s “I Can’t Quit You” was another straight steal by Zep, and WD’s original smokes the Zep version; “White Summer” is a rip of “She Moved Through the Fair” (the Davy Graham ‘raga’ version).
Oh, and the Stones ripped “Last Time” from the Staple Singers.
Some of this is attributable to way too much booze and whatnot, plus musicians tend to be carny trash. :^)