Getting a Google Map to display in an iframe on a Drupal site means following a very specific set of steps. Here's one solution, using the iframe module.
Embedding a Google Map via an iframe makes it very convenient for your viewers. The map displays well, and has helpful links: Directions, View in Google Maps, etc. This is tricky to do using standard Drupal input formats, but is made much easier with the iFrame module - which allows you to create an iframe field on any content type.