Countries worldwide have suffered from the battle with COVID-19 and its consequences. Many prevention and control strategies have been implemented to mitigate the spread. These measures include lockdown, quarantine, isolation, contact tracing, massive testing, and awareness programs to encourage people to adopt social distancing and maintain personal hygiene. As is always the case with infectious diseases, mathematical models have been used in order to gain insights into the dynamics of COVID-19 and assess the disease intervention practices for decision-making. Compartmental models have been constructed in this research to investigate the dynamics of COVID-19 from different aspects. The first model investigates the environ ment's role in the disease's transmission dynamics. The second model includes three different transmission routes, namely, asymptomatic, presymptomatic, and symptomatic transmissions, to investigate the role of presymptomatic individuals in the disease spread. The third model explores the role of diagnosis rate in the transmission dynamics, together with the combined effects of quarantine and isolation. The fourth model investigates the role of different types of quarantine and isolation in the disease transmission dynamics. The quarantine compartment is subdivided into short and long quarantine classes, and the isolation compartment is subdivided into tested and nontested home-isolated individuals and institutionally isolated individuals. The fifth model assesses the impact of placing healthy individuals in quarantine and isolating in fected ones on the number of hospitalization and intensive care unit cases. The analysis of the models includes positivity and boundedness of solutions, calculation of the basic and control reproduction numbers and their relation to all transmission routes. Moreover, existence, and stability analysis of disease-free and endemic equilibrium points, and bifurcation analysis are discussed. Model parameters have been estimated using data fitting approach. Sensitivity anal ysis of the reproduction number to model parameters has also been presented for each model. Finally, numerical simulations to demonstrate the effect of some model parameters related to the aspect considered in each model have been carried out, and the results have been demonstrated graphically.