Infrastructure automation is a crucial part of DevOps processes, enabling teams to manage workloads more efficiently and quickly deploy software. DevOps tools for infrastructure automation provide the necessary automation to streamline processes and reduce manual intervention. Key factors to consider when choosing an infrastructure automation tool include compatibility with existing infrastructure, features and functionality, ease of use, scalability, integration with other tools, support and documentation, and cost. The most useful DevOps tools for infrastructure automation are Terraform, Pulumi, AWS CloudFormation, Azure Resource Manager, AWS CDK, Google Cloud Deployment Manager, Ansible, Chef, Puppet, Spacelift, Jenkins, Spinnaker, Kubernetes, Nomad, Red Hat OpenShift, Packer, Vagrant, Prometheus, Sensu, and Nagios.