Metal nanoparticles (NPs) with antibacterial properties represent a promising alternative approach to antibiotics, whose overuse has led to the appearance of drug-resistant bacteria. This article addresses particularly copper (Cu) nanoparticles since Cu is a structural constituent of many enzymes in living microorganisms. In addition, Cu has better antibacterial effect and minimal cost compared to silver. The properties of Cu nanoparticles are described here: antibactericide, toxicity mechanisms, oxidation, and copper oxide biocompatibility for medical applications. Along with the advantages of Cu nanoparticles, the nanotoxicity still remains to take into consideration such as in targetting different bacteria strains, bacteria’s resistance, the effect of size, the effect of NP chemical composition, the effect of oxidation, and the corona phenomenon effect. The methodology of Cu nanoparticles synthesis, related to the biocidal effect, is illustrated by some limitations and some breakthrough such as chitosan stabilizer (CS), laser ablation, plasma induction, and flow-levitation method (FL). Although Cu nanoparticles are beneficial for bacterial elimination, these nanoparticles are graded harmful to the human body and the environment because of their toxic effects. Thus, it requires further improvement and further investigation to create super antibacterial Cu nanoparticles, to develop some interesting research work around this subject and to reveal some promising medical findings.