Invasion is an emerging but rapidly growing area of research in microbial ecology, with most studies focussing on the topic of biotic resistance. Biotic resistance is the ability of a native community to keep out invading species, and is usually explored through the lens of a diversity-functioning type rela- tionship. Biotic resistance is a particularly attractive concept to microbial ecologists, because it offers the potential to be used to understand how mi- crobial communities maintain stability over time. Such an understanding is relevant to microbial community assembly generally, and could also be used to understand how resident microbiomes help their hosts resist pathogen invasion, for example. However, biotic resistance studies have been largely limited to a focus on species diversity, whereas in natural communities many other factors influence biotic resistance. We use a series of experiments with artificial and natural microbial communities in order to understand what are the community traits other than simple diversity metrics that drive bi- otic resistance, and how other factors influence the role of biotic resistance in invasion success. Our key experiment is a common garden experiment with a large number of natural microbial communities, in which we seek to understand the relative roles of diversity, composition and function in inva- sion resistance. Additionally, we also perform experiments in which we try to apply biotic resistance concepts to understand how amphibian skin bac- teria resist the invasion of the amphibian chytrid fungus (Batrachochytrium dendrobatidis), an emergent fungal wildlife pathogen. We make the case for continued but expanded research into biotic resistance, and use our results to suggest directions for future research that are most likely to expand our understanding of biotic resistance more generally.