If we want to discuss the various metanarratives in White Teeth, we should probably make sure we know what "metanarrative" means. Without being too wordy, we could define metanarrative as a structure that brings together various details—seemingly big or small—as a way to explain or justify the overall fate of the characters and their stories.
Perhaps the English scholars John Stephens and Robyn McCallum put it better when they defined metanarrative as a "global or totalizing cultural narrative schema which orders and explains knowledge and experience."
A metanarrative probably won't just throw in a detail for any old reason. Like we said, a metanarrative organizes all of the details and experiences as a way to explain the behaviors and experiences of the characters.
One metanarrative in White Teeth involves Clara Jones and her daughter Irie. What happens when Clara and Ryan go on his scooter? They hit a tree, and some of Clara's teeth are knocked out. What does Irie end up choosing for her career? She ends up "opting for a life of dentistry."
Here, we see how the experience of Clara crashing into the tree could explain Clara's career choice to be a dentist. It's a metanarrative.
We also see a metanarrative in Archie's coin flips. How does Archie make crucial decisions? Through contemplation and introspection? No, by tossing a coin. How can a metanarrative encompass such a seemingly random act? Perhaps the metanarrative neutralizes the randomness of the coin flip. In Zadie Smith's metanarrative structure, the coin flip isn't so random. It has to play out a certain way. He had to go to that party and meet Clara.
Metanarrative also shows up in the facts about the birth of Magid and Millat. Magid is older. How much older? Two minutes. The 120 seconds organize Magid's life and Millat's life in major ways. It sends Magid to Bangladesh and Millat into Islamic fundamentalism.