יִרְעַ֤ם הַיָּם֙ וּמְלוֹא֔וֹ יַעֲלֹ֥ץ הַשָּׂדֶ֖ה וְכָל־אֲשֶׁר־בּֽוֹ׃
Let the sea roar, and the fulness thereof; Let the field exult, and all that is therein;
Tur HaArokh
וממגד ארץ ומלואה, “from the bounty of the land and its fullness;” this refers to the produce grown in the coastal plains, seeing that the produce growing on mountains and on hills has already been mentioned. Nachmanides explains the words as referring to blessings of the breast and womb respectively, corresponding to Yaakov’s blessing in Genesis He claims that every living creature is called מלואה inasmuch as they help fill the earth. He quotes as proof Chronicles I 16,32 ירעם הים ומלואו, “let the sea and all that is in it thunder.”
Rashi
he will not rejoice Heb. יעלס, with it. Similarly, יַעֲלֹז, and so יַעַלֹץ ; the three of them are interchangeable.