Metropolis[logpdf, logpdfjump, randomjump, x0, n] generates n Metropolis updates starting from x0. The target distribution is p[x] with the proposal distribution J[xt, x] randomized by x = randomjump[xt] given current xt. Here logpdf[x] = Log[p[x]] and logpdfjump[xt,x] = Log[J[xt,x]]