In the past years, the use of mechanochemistry to carry out solventless C鈥揌 functionalizations through the formation of metallacycles has gained ground in chemical synthesis and its applicability is expected to become more general. In this presentation, Jos茅 G. Hern谩ndez will give an overview of the topic, focussing on the mechanistic steps that lead to the activation of C鈥揌 bonds by mechanochemistry.