Glass-forming metallic systems are either simple and show a marginal glass-formation tendency with high transformation rates towards the crystalline state or the systems offer a high stability of the undercooled liquid state against crystallization, but are chemically complex. However, metallic systems can be utilized as model systems if the variations in kinetic stability are used as a tool to select appropriate alloy systems for a limited range of problems to be investigated. Here, marginal glass-forming AI-based metallic glasses were used to study the early stages of crystal formation. A bulk glass-forming Pd-based system provided sufficient kinetic stability against crystallization to allow analyzing the relaxation spectrum near the glass transition by modulation calorimetry. These measurements were analyzed in the framework of a fluctuation model of the glass transition. Finally, possible interrelations between the length scale of dynamic heterogeneities and structural heterogeneities in the deeply undercooled liquid are discussed. (C) 2010 Elsevier B.V. All rights reserved.