Neurodegeneration is a complex and multifaceted process leading to many chronic diseased states. Neurodegenerative disorders include a number of different pathological conditions, like Alzheimer's and Parkinson's diseases, which share similar critical metabolic processes, such as protein aggregation, which could be affected by some metal ions. A huge number of reports indicate that, among putative aggravating factors, metal ions (Al, Zn, Cu, Fe) could specifically impair protein aggregation of Abeta, prion protein, ataxin, huntingtin, etc. and their oligomeric toxicity. While studying the molecular basis of these diseases, it has become clear that protein conformation plays a critical role in the pathogenic process. In this review, we will focus on Alzheimer's disease and on the role of metal ions, specifically aluminium, in affecting amyloid aggregation, oligomerization and toxicity.