"Music shows us that all of it matters -- every story within every voice, every note within every song," said the former first lady, looking glam in a sparkling gunmetal pantsuit with a 1970s-esque wrap jacket.

"Is that right, ladies?" she said to resounding applause.

The #GRAMMYs are always full of surprises, but the crowd at the Staples Center was particularly taken aback when none other than @MichelleObama took the stage tonight. If you aren't tuned in, you are missing out!https://t.co/ee6wfCJkwh

— Recording Academy / GRAMMYs (@RecordingAcad) February 11, 2019

The Recording Academy behind the awards gala has faced a barrage of criticism for not embracing diversity within its ranks, after nearly muting women nominees at the show last year.

This year, five of the eight nominees for Album of the Year are women: rapper Cardi B, folk-rock singer Brandi Carlile, pop futurist Janelle Monae, R&B prodigy H.E.R. and country star Kacey Musgraves.

At the start of the segment, Lady Gaga -- a triple winner so far on the night -- said: "They told me I was weird... And music told me not to listen to them."

Lopez -- who has parlayed her successful music career into acting -- said that music "kept me moving from the block to the big stages and even bigger screens."

Pinkett-Smith added: "Every voice we hear deserves to be honored and respected."

Read also: Childish Gambino wins Song Of The Year Grammy for 'This Is America'

And Obama added: "Whether we like country or rap or rock, music helps us share ourselves, our dignity and sorrows, our hopes and joys. It allows us to hear one another, to invite each other in."

Obama quickly started trending on Twitter.

The moment came at the start of a show showcasing the female talent in the music business, one year after women were largely snubbed in the major categories.

Neil Portnow, the head of the Recording Academy, told women last year to "step up" if they wanted to do better on Grammys night. 

The brazen comment drew outrage and Portnow said he would step down when his contract expires this summer.

On Sunday, the message was unmistakable -- one of diversity.

"Thank you so much, ladies, for your light, your message of love, your sisterhood," said Keys, the first woman to helm the show in 14 years.

"Give it up for these magnificent goddesses!" said Keys.