Right-click the file and select "Scan with..."
Many .rar files are password-protected by the uploader. Check the page where you found the link; usually, the password is listed nearby (often the name of the website or a simple "123").
Before clicking any download links, make sure you trust the website. Files with .rar or .zip extensions are "containers" that can hold many different types of files, including harmful ones if the source isn't reputable.
Windows and macOS don't always open .rar files natively like they do with .zip files. You will likely need a specific tool to "extract" the contents: