Conjugative plasmids and integrative & conjugative elements are ubiquitous in bacteria. Through their horizontal transfer they facilitate single-step evolution of complex traits that might otherwise take millions of years to evolve. In the present era of microbial genomics, the hallmarks of horizontal gene transfer have become clearer and more abundant. However, our molecular understanding of the underlying mechanisms of gene transfer often lags. Using examples from my research career I summarise some of the complex and sometimes counterintuitive mechanisms by which conjugative elements facilitate and regulate gene transfer and ensure their persistence in prokaryotic genomes.