  We obtain KSS, Strichartz and certain weighted Strichartz estimate for the
wave equation on $(\R^d, \mathfrak{g})$, $d \geq 3$, when metric $\mathfrak{g}$
is non-trapping and approaches the Euclidean metric like $ x ^{- \rho}$ with
$\rho>0$. Using the KSS estimate, we prove almost global existence for
quadratically semilinear wave equations with small initial data for $\rho> 1$
and $d=3$. Also, we establish the Strauss conjecture when the metric is radial
with $\rho>0$ for $d= 3$.
