  We study the moduli of elliptic K3 surfaces with a section with the $ADE$
rank 17. While the Picard number of a generic K3 surface in such moduli space
is 19, the Picard number is enhanced to 20 at special points in the moduli. K3
surfaces become attractive K3 surfaces at these points. Either of the following
two situations occurs at such special points: i) the Mordell-Weil rank of an
elliptic K3 surface is enhanced, or ii) the gauge symmetry is enhanced. The
first case i) is related to the appearance of a $U(1)$ gauge symmetry. In this
note, we construct the moduli of K3 surfaces with $ADE$ types $E_7 D_{10}$ and
$A_{17}$. We determine some of the special points at which K3 surfaces become
attractive in the moduli of K3 surfaces with $ADE$ types $E_7 D_{10}$ and
$A_{17}$. We investigate the gauge symmetries in F-theory compactifications on
attractive K3 surfaces which correspond to such special points in the moduli
times a K3 surface. $U(1)$ gauge symmetry arises in some F-theory
compactifications.
