This is true in part. Iodine is a trace mineral, but iron is not.
Iodine is defined as a "trace element" because it is needed only in small amounts. The recommended daily allowance for iodine is only about 100 micrograms/day except in pregnant and lactating women who require about 300 micrograms/day. The main need for iodine is on the synthesis of the thyroid hormones and these in turn are needed to maintain the level of metabolic activity necessary to support life. They are also the development of the nervous and skeletal systems. Iodine deficiency can lead to hypothyroidism, a deficiency in the amount of thyroid hormones. Common symptoms of hypothyroidisms are sluggishness and sensitivity to cold among others.
For iron, the recommended daily allowance for iron is about 10-30 mg/day depending on your gender and age. Pregnant women require more iron than non-pregnant or lactating women or men. Iron is an important component of hemoglobin and myoglobin. Hemoglobin is a protein present in red blood cells that is required to carry oxygen in the blood. Because of this, iron deficiency can result in anemia. Myoglobin is present in muscle and is required to provide oxygen to muscle. There are other reasons why iron is needed in the body but these are the main two.