Rust fungi cause severe diseases in plants and are a major threat to cereal crop production and global food security. Central to the success of rust infection is the secretion of effector proteins, which function to manipulate the host plant. Here, we applied AlphaFold2 to predict structures for the secretomes of four cereal-infecting rust fungi, using the flax rust secretome (Melampsora lini) as an outgroup, to investigate conserved structural features. Using a comparative structural analysis, we identified conserved structural families within and across the rust species, with some expanded families including known rust avirulence (Avr) proteins. We benchmarked AlphaFold2 against our experimentally determined structure of AvrSr27 from Puccinia graminis f. sp. tritici (Pgt), which has a novel zinc-bound, duplicated domain structure. Although the AlphaFold2 predicted AvrSr27 structure was not completely accurate, we were able to identify the metal-binding sites. Using an established in silico screen for metal binding sites, we identified several other unrelated effector families that are also predicted to bind metal ions, including the recently cloned Pgt Avrs, AvrSr13 and AvrSr22. Predicted metal binding proteins account for about 13% of the secreted proteins of Pgt, suggesting that this is a common feature in rust effectors. As observed in flax rust, all five confirmed Pgt Avr proteins belong to different structural classes, indicating that rusts employ a more structurally diverse set of effectors than oomycetes and powdery mildew pathogens, whose effectors predominantly belong to a single class (WY and RALPH, respectively).