The sublime-text-gleam package provides Gleam syntax highlighting is available on package control, to install it:

  1. Open the command palette (Ctrl/Cmd+Shift+P)
  2. Select Package Control: Install Package
  3. Select Gleam

The LSP package can be configured to use the Gleam language server. Open "Preferences: LSP Settings" in the command palette, and then add this config:

{
  "clients": {
    "gleam": {
      "enabled": true,
      "command": ["gleam", "lsp"],
      "selector": "source.gleam"
    }
  },
  "lsp_format_on_save": true
}

For more information see the documentation.