Mutt has a builtin line editor which is used as the primary way to input textual data such as email addresses or filenames. The keys used to move around while editing are very similar to those of Emacs.
A or <Home> bol move to the start of the line
^B or <Left> backward-char move back one char
Esc B backward-word move back one word
^D or <Delete> delete-char delete the char under the cursor
^E or <End> eol move to the end of the line
^F or <Right> forward-char move forward one char
Esc F forward-word move forward one word
<Tab> complete complete filename or alias
^T complete-query complete address with query
^K kill-eol delete to the end of the line
ESC d kill-eow delete to the end ot the word
^W kill-word kill the word in front of the cursor
^U kill-line delete entire line
^V quote-char quote the next typed key
<Up> history-up recall previous string from history
<Down> history-down recall next string from history
<BackSpace> backspace kill the char in front of the cursor
Esc u upcase-word convert word to upper case
Esc l downcase-word convert word to lower case
Esc c capitalize-word capitalize the word
^G n/a abort
<Return> n/a finish editing
You can remap the editor functions using the bind command. For example, to make the Delete key delete the character in front of the cursor rather than under, you could use
bind editor <delete> backspace