Together with partners and out of its own portfolio, Microsoft offers a wide range of extensions for VMs. Those extensions range from simple anti-malware solutions and backup, to deployment extensions for desired state configuration, to open source plugins such as those for the Chef server or Puppet.
The following screenshot shows some of the extensions:
The number of extensions for VMs is rapidly growing. To get a full and accurate list, you need to run the following PowerShell command in Microsoft Azure:
Get-AzureVMAvailableExtension | Select ExtensionName, Version
The VM extensions are already delivered with a license for the product and the cost for that license will be calculated together with your virtual machine costs. Even with the license not purchased by yourself, you can include those extensions in your central management, for example, when it comes to anti-malware.