Examples allocating resources to virtual network functions (VNFs). Some examples include monitoring information associated with a set of VNFs that includes a set of VNF instances. A resource allocation event may be predicted for a VNF instance based on the monitored information and a resource flexing model that is developed using a capacity metric of the VNF instance. A resource flexing plan may be generated based on the resource allocation event and an order of the set of VNFs in a service function chain.