Metal nanostructures concentrate optical fields into highly confined, nanoscale volumes that can be exploited in a wide range of applications. However, the use of plasmonic structures as cavities for generating coherent emission seems counter-intuitive based on conventional designs of macroscopic lasers. This talk will describe how arrays of nanoparticles can support a unique open-cavity architecture that can be used to interrogate the mechanisms of energy transfer processes and plasmon amplification in confined systems. First, we will describe how single band-edge lattice plasmons in metal nanoparticle arrays can contribute to single-mode lasing at room-temperature with directional emission. Second, we will discuss how ultra-narrow resonances from superlattice plasmons, collective excitations in hierarchical nanoparticle arrays, can support multi-modal nanolasing. Finally, we will describe challenges in and approaches to differentiating among competing energy transfer in the lasing action based on coherence, cavity size, and ultra-fast characteristics.