The theme of Rihanna’s “Last Girl on Earth” tour, as suggested by its recurring video images of computers downloading her dreams, is the subconscious, which is always more interesting than the conscious. Isn’t it?

Rihanna’s, according to the vibe of the show, contains sex, the will to domination and revenge. But it’s a good chance that yours does too, even if you have never met her ex-boyfriend, Chris Brown.

In her show at Madison Square Garden on Thursday night, she bestrode a pink tank’s gun turret while wearing a Mouseketeer helmet; smashed the husk of an old car and entreated a young female fan to do the same; played a flying-V electric guitar — crudely, imperiously — from atop a tall platform; sang in front of trapeze artists hanging from giant rifles; and spent a lot of time in a black latex unitard with fabric at the haunchesand high boots. Love is a battlefield. Love is a circus. Love is a strip club.

None of this cut very deeply, and not just because these themes are so incredibly banal, but because Rihanna keeps her affect on lockdown. She spoke little. That vibrato shake at the end of her vocal lines is about the sum of her charm as a singer. She moved in smooth, even glides. Her low hip-grind in “Rude Boy” and her lip curl in “Rehab,” as she reclined on a hideous therapist’s couch, adorned with metal casts of human heads and limbs: these were the smash hits of her body language. (Most at the Garden could see her snarl only via overhead video screens, which also picked up clear angles of her new Francophone neck tattoo.)

Rihanna, now 22, hasn’t been with us that long: four albums and five years, though it’s only the last three that have particularly mattered, with hits like “Don’t Stop the Music,” “Disturbia,” “Rude Boy” and “Umbrella,” the song that swallowed 2007. (“Last Girl on Earth,” whose current dates include Kesha and Travie McCoy as opening acts, is her first headlining tour of North America.)

That’s more than twice as long a reign as Lady Gaga’s, but perhaps not long enough for the kind of full text-and-subtext, hit-after-hit, Madonna-Mariah-Beyoncé-level concert she aspires to. Thursday’s show was about angles and surfaces and still tableaus, borrowing visually from fashion, art and photography of the early 1980s, and musically from New Wave, disco and metal, via the feckless guitar shredding of Nuno Bettencourt. (If you squint, you might make a connection between her high-heeled assault on the car and the kind of thing Wendy O. Williams used to do on stage with the Plasmatics.)

It was also a show about optical illusions, about flat surfaces and volume against various backgrounds, about cheekbones and haunches and heels and hair. Unless you spent the evening reading along to her lyric sheets, it didn’t particularly leave you thinking about the aftermath of an abusive relationship, a theme underlined by “Rated R,” her recent album. It didn’t leave you thinking about cultural appropriation or what-would-she-dream-up-next. It left you thinking: how do they make her look so tall? And how tall is she, really?

Rihanna’s set was preceded by one from Kesha (who renders the s in her name as a dollar sign) that felt far less guarded and in some places more purely joyous. (And if you can’t believe that a show involving a phallic gun-turret could be described as guarded, you weren’t there.) Kesha also juxtaposes girl-centered electronic pop with guy-rock stereotypes: she wore a sleeveless Metallica T-shirt and started out playing, or at least holding, a rifle-shaped guitar.

But Kesha’s act encompasses fantastic chants on the choruses; her stylized whine-talking through verses in a half San Fernando Valley, half mid-South delivery; rag-bag visuals (a skanky-looking dance crew, a rumpled American flag against a skinny bank of lights); and a super-low sense of humor that comes with mysterious confidence and self-possession.

Watching her sing “Tik Tok,” “Your Love Is My Drug” and “Party at a Rich Dude’s House” — all of them about getting dangerously wasted, literally or figuratively — you didn’t feel bad for her or for yourself. The songs are too good. She’s controlling her iconography as much as Rihanna does, tanks not included.