Based somewhat on Cash's real life, it follows him through his formative years as he loses his brother to a sawmill accident, and then joins the Air Force. Later on, he returns to the U.S. and tries to work as a salesman, but ends up signing to Sun Records because his heart is in the music business. Along the way, he marries and then divorces his first wife, Vivian (Ginnifer Goodwin), then meets and befriends June Carter (Reese Witherspoon). After some drug-induced tumult, he eventually cleans up and performs his now-legendary concert at Folsom Prison. Johnny and June then perform a concert in Canada, where he interrupts a song to propose to her. She accepts. (No, this wasn't a Hollywood romance ending. That really did happen.)
Both Phoenix and Witherspoon did all of their own singing and instrument-playing for the film. Among its awards, the film won one Academy Award (Best Actress for Witherspoon) and was nominated for three more (Best Actor for Phoenix, Best Sound, Best Costume Design, Best Film Editing).
One noted critic of the film was Rosanne Cash, Johnny's daughter from his first marriage, who said it was "painful"; Rosanne had a very good relationship with her stepmother June, and even spoke at her funeral. Mangold justified the somewhat unflattering portrayal of Rosanne's mother Vivian by saying that as a character, she was being seen from Johnny's perspective as he fell in love with June.
Walk the Line provides examples of:
- Anachronism Stew: J.R. and Jack, in 1944, quote the Foghorn Leghorn cartoon "All Fowled Up" - which was not released until 1955, and Foghorn himself did not debut until 1946.
- Artistic License – History:
- The movie makes it look like Jack Cash's death occurred on the same day that he was cut almost in half by a tablesaw. In real life, he suffered for over a week before he died.
- In real life Johnny's drug rehabilitation was a much more drawn out endeavor. While he did detox at the Cash house (attended to by June and her parents), it just brought his drug use down to a manageable level. Case in point, he was high when he recorded Live at Folsom Prison. He continued to abuse pills up until the birth of his son in 1970, two years after the movie ended, and didn't clean up for good until 1992.
- Artistic License – Music: Referenced by Cash, who said that he hoped that whoever played him would at least know how to hold a guitar. He did.
- Brick Joke: "I got the laryngitis!"
- Cool Old Guy and Never Mess with Granny: While Johnny is undergoing his self-imposed detoxification, his dealer, unaware that anything was going on, shows up at Johnny's house with his supply of pills. The dealer is met by Johnny's future father-in-law Ezra Carter, with a shotgun. Backing up Ezra was his wife "Mother" Maybelle. With her own shotgun.
- Foregone Conclusion: Anyone who is familiar with country music in general would know that Johnny Cash would overcome his drug addictions (eventually), his Folsom Prison concert would be a success, and he eventually marries June Carter.
- Good Adultery, Bad Adultery: Johnny Cash is distant and generally a dick to his first wife, while openly pursuing June Carter who, by contrast, is entirely unwilling to betray her husband. But he's portrayed sympathetically, and he finally winds up with her. He is Johnny freaking Cash though.
- Happily Ever Before: The film ends at Cash's performance of his Folsom Prison Album and marriage to June in 1968 at perhaps the height of his career commercially and only the beginning of his "superstar" period. He would go on to have a son with June (John Carter), play another prison album (San Quentin), and do more big shows like Madison Square Garden, but he would also relapse into addiction and suffer marital troubles. He'd eventually be dropped by Columbia Records and essentially be forgotten by his Mercury label before a resurgence under producer Rick Rubin, but by that point he'd be near the end of his life while enduring immense pain, stuck in a wheelchair and nearly blind. Almost enough material for a sequel.
- Heel–Faith Turn: Johnny goes through one of these, although it is shown subtly. As Johnny descends deeper into his adulterous and drug-filled career, he shows an aversion to religion and praying. Following his detox, June takes him to a church service. He hesitates, but walks in after being encouraged by June.
- Historical In-Joke: Although they are harsher in hindsight.
- When Johnny Cash wakes up on the tour bus, he walks past a passed out Luther Perkins (his guitarist) with a lit cigarette in his mouth, and he casually puts it out. Perkins dies months after the "At Folsom Prison" recording/performance when he fell asleep in his Tennessee home with a lit cigarette in his mouth, succumbing to burn injuries sustained in the resulting fire.
- Similarly, Elvis Presley offers Johnny amphetamines and cheese fries, two of the things that would help lead to "The King"'s own heavyset phase and early death.
- Historical Villain Upgrade: In order to make Johnny's character seem more sympathetic, his first wife is shown disapproving of his early attempts to break into the music business, urging him to give it up and focus on getting a better job from her father. According to the real Johnny's autobiography, she was actually extremely supportive of his musical ambitions, and their marriage problems did not start until after his career took off. Also applies to Johnny's dad. The real Johnny mentioned that his dad was rather distant and a man of few words, not a raging dick like he is in this film. Although by the end of the movie, they have clearly reconciled.
- Meaningful Echo: Several lines, including the page quote.
- Non Sequitur, *Thud*:
- As he loses consciousness after collapsing onstage, Johnny mutters, "Fortunately, I keep my feathers numbered for just such an occasion" (an old Foghorn Leghorn line).
- Doubles as a Meaningful Echo, as Johnny was telling his brother about that cartoon shortly before the latter's death.
- Oscar Bait: Accused of being this; though it has many of the elements of the genre including historical figures and drug addictions.
- Please, Don't Leave Me: These are the exact words J.R. says to his dying brother.
- Precision F-Strike:
- Cash generally sticks only to the mild, old-school country boy stuff like "damn" and "hell". But in the scene where he performs on stage drunk/high, he acts very strange, playing the guitar with a dazed smile on his face and making an unusually harsh aside to his drummer: "Play the fucking thing." Moments later, he collapses. This surprising usage of the word catches the viewer and the band off-guard and lets them know something bad is about to go down.
- At Folsom Prison, he remarks that the concert is being recorded for an album, "so you can't say 'hell' or 'shit' or anything like that." This comment appears on the actual album, although the LP had the latter bleeped out.
- Race Lift: Vivian Cash had slight African-American ancestry (one of her maternal great-great-grandmothers was a mixed-race slave later freed by her father); this, along with her Italian grandparents and her tanned complexion, led to a campaign of racist attacks on her claiming she was a black woman married to a white man (a major no-no in the South of the 50s and 60s). In the film she's played by the totally Caucasian and very pale actress Ginnifer Goodwin.
- "The Reason You Suck" Speech: June tends to give these to John, very effectively.
- Viv delivers a couple to Johnny as well, only they don't take.
- Running Gag: Johnny repeatedly asks June to marry him. It never goes over well. Except for the last time.
- Shout-Out: The line, "Fortunately, I keep my feathers numbered for just such an emergency" comes from the 1955 Foghorn Leghorn short "All Fowled Up".
- Shown Their Work: Phoenix and Witherspoon learned to sing and play guitar and autoharp, respectively, for their roles. Witherspoon also looked through June Carter Cash's closet for inspiration. According to music supervisor and legendary producer T-Bone Burnett, Phoenix had so much trouble getting to Cash's iconic tone that they nearly resigned themselves to dubbing him over before Phoenix's voice dropped to the correct octave a week before shooting. Phoenix also had difficulty with his breathing before watching some of Johnny's live performances. Cash's idiosyncracy of tilting his head back after each line was a way of straightening his throat so he could take in a full breath quicker than if he'd kept his head in a normal position.
- Title Drop: June says "Y'all can't walk no line" in one scene. Oh yes, and there is the fact that Cash recorded a song called "I Walk the Line."
- Traveling Salesman Montage: There's one of these early in the film to illustrate just how bad John is as a salesman.
- The Un-Favourite: Johnny never could quite match up to his dutiful dead brother, Jack, in his dad's eyes.
- "Well Done, Son" Guy: Johnny's father, partly due to Johnny's aforementioned status as the unfavored son.
- You Are Better Than You Think You Are: When Johnny is recovering, he is surprised that June and her family are helping him despite everything he has done to her. June tells him he’s a good man despite it all.