Swedish is a member of the Germanic branch of the Indo-European family and therefore shares close ties with English. Swedes tend to learn English relatively easily. Since Swedish, Danish and Norwegian are closely connected, much of the following analysis applies to the latter two languages too, particularly in terms of grammar.
The Swedish phonological system is similar to that of English. Swedish has about 17 pure vowel sounds, rather more than English. This certainly facilitates the production of correct-sounding English words. Nevertheless, Swedes do have some problems with minimal pairs such as ship / sheep or bed / bad.
There are about 18 consonant phonemes, which show considerable overlap with those of English. The most common difficulties are with the English th words (three, think, clothes, then etc.). Words such as leisure and laser are often mispronounced as lesher or lacer.
Like English, Swedish is a stress-timed language and has similar intonation patterns. However, there are differences that may negatively transfer when Swedes speak English. For example, they may overstress words that typically English native speakers would swallow, such as the, but, was, have. Swedish, unlike English, is a tone language. This means that it can distinguish word meanings by differences in pitch. This may result in the production of statements in English that sound like questions or sentences that sound incomplete (particularly sentences ending with a two-syllable word).
The English and Swedish verb systems share many features, so learning English verb grammar is not unduly difficult for Swedish students. Problematic for beginning learners is the use of the auxiliary do in English questions and negative statements. One significant difference between the two languages is the absence in Swedish of the continuous tense. This leads beginning learners to produce sentences such as She does her homework now, or to overcompensate: In Sweden everyone is playing winter sports. Swedish is uninflected; possibly for this reason even some very proficent speakers of English speakers omit the -s ending in the third person of the present simple tense: My mother work in a bank.
The existence of an identical tense form in two languages (for example, a tense that uses have as an auxiliary, together with a past participle) is no guarantee that the tenses will be used in the same situations. This is true also of Swedish and English. Swedish, for example, uses the present perfect in cases where English requires the past simple. Interference will lead to errors such as: I have stopped playing tennis when I have broken my leg. Another example is in talking about the future. Swedish uses the present simple where English needs the auxiliaries will or going to, resulting in: I wait for you after school / I think it rains.
Swedish is a Subject-Verb-Object language like English, so mistakes in word order tend not to impede comprehension. In Swedish, however, it is more common to bring an element to the front of the sentence and then invert subject and verb (as in German). Negative transfer can result in sentences such as: My dictionary have I forgotten. The construction there + verb is common in Swedish, whereas in English it is mostly restricted to there + to be. This may lead to faulty statements such as: There came a lot of students to the dance.
Other common grammar mistakes that are probably the result of interference include:
the use of adjectives rather than adverbs: She sings very good
the use of the definitive article where English would omit it: I don't like the spiders
overuse of the genitive -s: the car's door / the food's smell
In view of the close relationship between the two languages, it is not surprising that Swedish and English have many cognates that can facilitate reading comprehension and efficent vocabulary-building. False friends, the negative counterpart of cognates, include control (Swedish: check) / luck (Swedish: happiness) / take place (Swedish: sit down). Another minor area of interference is the fact that some words that are plural in English are singular in Swedish (or vice versa): I need informations about .. / Let me give you an advice .. .