Massive stars are important in many astrophysical contexts. They dominate the energy and momentum budget of the interstellar medium and they enrich their surroundings with newly processed chemical elements, which constitute the building blocks of planets and life. Most massive stars are found in close binary systems and will interact with their companion during their lifetime, resulting in a variety of exotic products including X-ray binaries and gravitational wave sources. However, it is very challenging to understand the formation mechanism of massive stars and the origin of their high multiplicity because of their very short formation timescales, large distances, and them being embedded in their natal clouds. Additionally, more than half of all stars and planetary systems form in massive star forming regions where they are exposed to intense UV radiation from the nearby massive stars. Thanks to the unprecedented capabilities of JWST, we can now study the physical and chemical properties of proto-planetary disks in massive star-forming regions. 

In this colloquium I will present recent results concerning the formation of massive stars, including the disk and photospheric properties of pre-main sequence stars and the evidence of migration as the formation mechanism for massive binaries.I will also present the results of a JWST program that I am leading (the XUE collaboration), where we are exploring the impact of external UV radiation on the disk structure, warm disk chemistry, and dust mineralogy, all of which are important for planet formation models and exoplanet atmosphere composition.