Gravity Forms is an excellent plugin for adding forms to your WordPress site. It lets you do this easily and quickly and includes many options for functional changes to forms.
For some reason, the plugin does not allow removing the Submit button from its forms, so if you want to use it and embed your own button you will need to remove the plugin’s default button. Add the following line to your functions.php file:
add_filter( 'gform_submit_button', '__return_false' );For more form customization tips, see Restrict Free Emails in Forms.