An IAM role is a container for a policy. Using IAM roles for EC2 instances allows for easy management of access keys and for their automatic rotation, that is, Amazon rotates the keys several times a day without requiring any specific action from your end. Hence, you should not have the access keys as a part of the AMI or your application, as their rotation becomes unnecessarily complicated. We just need to create an IAM role, assign permissions to the role, and then launch the EC2 instances to make this work.
After creating a role, you will also need to create a policy and assign it to the newly created role. For example, if an EC2 instance needs access to other AWS services, such as S3 buckets or DynamoDB tables, then you can create a role for it. You will assign the role permissions that allow access to S3/DynamoDB, and finally launch the EC2 instance with that role. You can create one role and attach it to multiple EC2 instances.
