As I mentioned, the Grand Palais and Petit Palais were specially designed to host art exhibitions, and they have essentially retained this role, though they have been through various ups and downs over the 20th century. Their architecture is still in the gray area between the desire for renewal and academic tradition.
We certainly can't say that the buildings were named with a stroke of genius! The Grand Palais, or "Large Palace", is made entirely of glass and steel and is substantially based on railway engineering; it's not much different from the platforms built for the Orsay station, which is also connected to the Expo of the year 1900. But what's surprising about this monument is that its modern "heart" resembles traditional architecture in refined stone, which even reminds you of the Neoclassical canons. In short, it matches the "Parisian" taste for grandeur, but is a bit dated and unfashionable for 1900.
Its long façade is preceded by a grandiose portico, and you'll probably find the whole quite monotonous even if it offers pleasant decorative surprises here and there that belong to the so-called Art Nouveau style, such as the lovely ornamental statues and beautiful wrought iron gate.
Once inside, another thing you might not expect is the steel staircase that leads you to an immense space covered by the iron vault with windows. You should also bear in mind that although it was created as an exhibition venue for art, the Grand Palais has hosted other kinds of exhibitions and fairs in its time, ranging from horses to cars.
In 1993 a sheet of its cladding broke off and fell, fortunately without harming anyone, but revealing that the structure was already poorly off even though it wasn't even a hundred years old. After twelve years of restoration and modernization it was reopened, again serving its original role as a venue for figurative arts exhibitions. If you'd like, you can also dine in its restaurant located in a scenic hall with columns.
FUN FACT: in 1907 the Grand Palais hosted an exhibition dedicated to the painter Paul Cézanne, who lived in the countryside and was relatively unknown in Paris. The exhibition had a profound effect on the art of the early 1900s: both Pablo Picasso and Henri Matisse visited it together and were shocked. When leaving, Matisse said, "He was a great master", and Picasso replied: "No, he was our father!" From then on, both men changed their style.