Within the Large Magellanic Cloud, a hot core is observed associated with the embedded high-mass YSO (IRAS 05195˗6911), known as ST16. Comparative observations with molecular abundances typical of Galactic hot cores are discussed, as is the evidence for a rotating protostellar envelope and outflow cavity. A second LMC source, the prominent star-formation region N113, shows centrally focused star formation with associated point-like mid-infrared emission, masers, and compact HII regions superimposed on extended emission. Gas and dust appear compressed by a complex structure of ionized gas bubbles (prominent in Hα detections) engendered by massive stars in several young clusters. In both ST16 and N113 low-metallicity sources, warm dust appears to inhibit COMs formation and survival, while reaction routes appear broadly comparable with Galactic models.

The three UCHII regions associated with the G34.26+0.15 high-mass star formation complex in Aquila are described, giving evidence for envelope infall, protostellar outflows, expanding ionized gas, and associated molecular hot core chemistry. The prototypical ‘cometary’ UCHII region ‘C’ in G34.26 is one focus, where the interface between ionized hydrogen (HII) and hot molecular core (HMC) gas is well observed and a rich hot core chemistry both detected and modelled in detail. Uncertainties in CH3CN formation, and the displacement of its peak emission from dust and NH3 peaks, are raised in relation to possible photodissociation in the hot core close to the UCHII-C feature.

The massive giant molecular cloud (GMC) complex Westerhout 43 (W43) and its subcores are considered, in particular G29.96. HMSF is evident in clusters and the impact of disk winds and outflows on the observable chemistry made clear. Modelling of the hot core COMs abundances matches observations for many key species observed in both this and other Galactic sources. The interaction between an HII region and an associated hot dense core is exemplified in G29.96, in spite of the evident complexity of physical conditions in the surrounding region. As in all studies made through the lens of molecular emission, astronomers are able to probe the physical conditions through trace chemical emissions.

The G24.78+0.08 source is examined as a multiple core and sub-core complex in which both ultra- and hyper-compact HII locations are identified, along with outflows, accretion disks, and hot cores. Molecular emission lines as well as radio recombination lines (RRLs) and free–free emission offer evidence for thermal, pressure, and dynamical (including infall and rotation) kinematics. Molecular line signatures trace HII/hot core interactions, and also enable estimates of the physical parameters of HMSF accretion disks (such as density, temperature, mass, and radius).

The unusual HMSFR Orion Becklin-Neuberger (Orion BN/KL) at the heart of the Orion Molecular Cloud-1 (OMC-1) is examined, with its associated explosive outflow of gas and dust. Its four well-studied features are the Hot Core, Compact Ridge, Plateau, and Extended Ridge. These sources offer much evidence for the sequential chemical processing of shocked molecular cloud material and indicate just how violent the dynamic processes associated with HMSFRs can be.