Use uma junção externa esquerda:
SELECT b.id as id, g.date
FROM `biometrics` as b
LEFT OUTER JOIN `users goals` as g ON biometricid = b.id and userid = $user->id
Bons exemplos de diferentes tipos de junção podem ser encontrados aqui .
SELECT b.id as id, g.date
FROM `biometrics` as b
LEFT OUTER JOIN `users goals` as g ON biometricid = b.id and userid = $user->id
