The first time the painter Jordan Casteel saw the dress Charles Elliot Harbison designed for her to wear to this year’s Met Gala, she immediately started to cry.

“Not only was it beautiful to see this garment that is tailored quite literally for me,” she said from her couch after her final fitting for what will be her first time attending the event. “It is something that feels like they were thinking about me from the beginning to the end in designing it.”

“This is a fever dream,” she added.

While Ms. Casteel had seen sketches and mood boards and was in constant communication with Mr. Harbison during the design process, the abstract came to life when she was in the room with the garment and the several tailors who were pinning and pricking the dress to her specific needs.

“I feel feminine, I feel bold,” she said about wearing the gown. “This is a moment where our freedom — there’s the complexities of the world that we exist in, but for this day for this carpet for this moment, we are showing up and this outfit makes me feel like I am stepping into a version of myself that no one would expect but that I know I belong.”

She added, “I feel I am powerful and I am beautiful and you will see me, my Black body is going to be seen.”

Ms. Casteel, 36, describes the dress as Afro-futurism, or “the things that we imagine for ourselves,” she said. “When I put it on, I think it’s the feminine part that feels really good.”

The dress is really a two-piece: a skirt and a top. They both have strong volume points around the hip and Ms. Casteel is expecting to reveal more and more of it as the night goes on. And while the dress is a focal point of the night, it is what will not be seen from the red carpet that she feels proudest to wear.

Beneath the dress will be a necklace that belonged to Ms. Casteel’s grandmother, Margaret Buckner Young, who was an author, educator and the first Black woman to serve on the board of the Metropolitan Museum of Art.

“We are all thinking about the dandies in our life,” Ms. Casteel said, referring to the theme of the gala this year. “She fashioned herself. I am holding her spirit as close as humanly possible in this moment.”

“This is for her,” she added. “That is also the freedom.”