G-protein coupled receptors (GPCR) are ubiquitously expressed membrane proteins which are activated by endogenous ligands and involved in a variety of biological functions. The Class B of GPCR receptors have a broad range of regulatory metabolic effects and are therefore important drug targets. Recent advances in cryo-electron microscopy (cryo-EM) have enabled us to study the structures of a variety of Class-B GPCR complexes with different ligands in their active states, and these structures help us understand the molecular mechanisms of these receptors and their transducers. Here, we report high-resolution structures of active Class B GPCR complexes to 2.3-2.7 Å average resolution, revealing atomic details of receptor-ligand and receptor-transducer interactions. Such resolution enables accurate placement of coordinated water networks into our maps. Using our cryo-EM data, we are not only able to build the static atomic models of the GPCR complexes, but we also identify dynamic subunits and the modes of flexibility using 3D variability analysis in CryoSPARC as well as focused refinements. Of particular interest is the high flexibility of the extracellular domains and loops of the receptors, which hints to their importance in initial ligand engagement prior to receptor activation. Our dynamic cryo-EM data is supported by further analysis using molecular dynamics simulations as well as mutations and cross-linking studies to pinpoint the important domains and residues for receptor activation and function. Our collective structural information offers a pathway to drug development for a variety of receptors involved in metabolic diseases.