One operation that we have to do fairly often when editing text is manipulating the case of words. The most popular case manipulations are probably capitalize, convert to lowercase and convert to uppercase. Emacs naturally has built-in commands for all of those.

Pressing M-c runs the command capitalize-word, which will capitalize the next word and move the cursor after it. Pressing M-- M-c will capitalize the previous word without moving the cursor.

Pressing M-l runs the command downcase-word, which will lowercase the next word and move the cursor after it. Pressing M-- M-l will lowercase the previous word without moving the cursor.

Pressing M-u runs the command upcase-word, which will uppercase the next word and move the cursor after it. Pressing M-- M-u will uppercase the previous word without moving the cursor.